Phosphor and light-emitting equipment using phosphor

ABSTRACT

Phosphors include a CaAlSiN 3  family crystal phase, wherein the CaAlSiN 3  family crystal phase comprises at least one element selected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/626,372, filed Jun. 19, 2017, now allowed; which is a division ofU.S. patent application Ser. No. 14/736,487, filed Jun. 11, 2015, nowU.S. Pat. No. 9,738,829; which, in turn is a continuation of U.S. patentapplication Ser. No. 13/775,334, filed Feb. 25, 2013; which, in turn isa continuation of U.S. patent application Ser. No. 11/441,094, filed May26, 2006, now U.S. Pat. No. 8,409,470; which, in turn is acontinuation-in-part of International Patent Application No.PCT/JP04/17895, filed Nov. 25, 2004, the disclosures of which areincorporated herein by reference in their entireties. This applicationclaims priority to Japanese Patent Application No. 2003-394855, filedNov. 26, 2003, Japanese Patent Application No, 2004-041503, filed Feb.18, 2004, Japanese Patent Application No. 2004-154548, filed May 25,2004, and Japanese Patent Application No. 2004-159306, filed May 28,2004, the disclosures of which are incorporated herein by reference intheir entireties.

FIELD OF THE INVENTION

The present invention relates to a phosphor mainly composed of aninorganic compound and applications thereof. More specifically, theapplications relate to light-emitting equipments such as a lightingequipment and an image display unit as well as a pigment and anultraviolet absorbent, which utilize a property possessed by thephosphor, i.e., a characteristic of emitting fluorescence having a longwavelength of 570 nm or longer.

BACKGROUND ART

Phosphors are used for a vacuum fluorescent display (VFD), a fieldemission display (FED), a plasma display panel (PDP), a cathode ray tube(CRT), a white light-emitting diode (LED), and the like. In all theseapplications, it is necessary to provide energy for exciting thephosphors in order to cause emission from the phosphors. The phosphorsare excited by an excitation source having a high energy, such as avacuum ultraviolet ray, an ultraviolet ray, an electron beam, or a bluelight to emit a visible light. However, as a result of exposure of thephosphors to the above excitation source, there arises a problem ofdecrease of luminance of the phosphors and hence a phosphor exhibitingno decrease of luminance has been desired. Therefore, a sialon phosphorhas been proposed as a phosphor exhibiting little decrease of luminanceinstead of conventional silicate phosphors, phosphate phosphors,aluminate phosphors, sulfide phosphors, and the like.

The sialon phosphor is produced by the production process outlinedbelow. First, silicon nitride (Si₃N₄), aluminum nitride (AlN), calciumcarbonate (CaCO₃), and europium oxide (Eu₂O₃) are mixed in apredetermined molar ratio and the mixture is held at 1700° C. for 1 hourin nitrogen at 1 atm (0.1 MPa) and is baked by a hot pressing process toproduce the phosphor (e.g., cf. Patent Literature 1). The α-sialonactivated with Eu obtained by the process is reported to be a phosphorwhich is excited by a blue light of 450 to 500 nm to emit a yellow lightof 550 to 600 nm. However, in the applications of a white LED and aplasma display using an ultraviolet LED as an excitation source,phosphors emitting lights exhibiting not only yellow color but alsoorange color and red color have been desired. Moreover, in a white LEDusing a blue LED as an excitation source, phosphors emitting lightsexhibiting orange color and red color have been desired in order toimprove color-rendering properties.

As a phosphor emitting a light of red color, an inorganic substance(Ba_(2−x)Eu_(x)Si₅N₈: x=0.14 to 1.16) obtained by activating a Ba₂Si₅N₈crystal phase with Eu has been reported in an academic literature (cf.Non-Patent Literature 1) prior to the present application. Furthermore,in Chapter 2 of a publication “On new rare-earth doped M-Si—Al—O—Nmaterials” (cf. Non-Patent Literature 2), a phosphor using a ternarynitride of an alkali metal and silicon having various compositions,M_(x)Si_(y)N_(z) (M=Ca, Sr, Ba, Zn; x, y, and z represent variousvalues) as a host has been reported. Similarly, M_(x)Si_(y)N_(z):Eu(M=Ca, Sr, Ba, Zn; z=2/3x+4/3y) has been reported in U.S. Pat. No.6,682,663 (Patent Literature 2).

As other sialon, nitride or oxynitride phosphors, there are known inJP-A-2003-206481 (Patent Literature 3) phosphors using MSi₃N₅, M₂Si₄N₇,M₄Si₆N₁₁, M₉Si₁₁N₂₃, M₁₆Si₁₅O₆N₃₂, M₁₃S₁₈Al₁₂O₁₈N₃₆, MSi₅Al₂ON₉, andM₃Si₅AlON₁₀ (wherein M represents Ba, Ca, Sr or a rare earth element) ashost crystals, which are activated with Eu or Ce. Among them, phosphorsemitting a light of red color have been also reported. Moreover, LEDlighting units using these phosphors are known. Furthermore,JP-A-2002-322474 (Patent Literature 4) has reported a phosphor whereinan Sr₂Si₅N₈ or SrSi₇N₁₀ crystal phase is activated with Ce.

In JP-A-2003-321675 (Patent Literature 5), there is a description ofLxMyN_((2/3x+4/3y)):Z (L is a divalent element such as Ca, Sr, or Ba, Mis a tetravalent element such as Si or Ge, and Z is an activator such asEu) phosphor and it describes that addition of a minute amount of Alexhibits an effect of suppressing afterglow. Moreover, a slightlyreddish warm color white emitting apparatus is known, wherein thephosphor and a blue LED are combined. Furthermore, JP-A-2003-277746(Patent Literature 6) reports phosphors constituted by variouscombinations of L Element, M Element, and Z Element asLxMyN_((2/3x+4/3y)):Z phosphors. JP-A-2004-10786 (Patent Literature 7)describes a wide range of combinations regarding an L-M-N:Eu,Z systembut there is not shown an effect of improving emission properties in thecases that a specific composition or crystal phase is used as a host.

The representative phosphors in Patent Literatures 2 to 7 mentionedabove contain nitrides of a divalent element and a tetravalent elementas host crystals and phosphors using various different crystal phases ashost crystals have been reported. The phosphors emitting a light of redcolor are also known but the emitting luminance of red color is notsufficient by excitation with a blue visible light. Moreover, they arechemically unstable in some compositions and thus their durability isproblematic.

[Non-Patent Literature 1]

H. A. Hoppe, and other four persons, “Journal of Physics and Chemistryof Solids” 2000, vol. 61, pages 2001-2006

[Non-Patent Literature 2]

“On new rare-earth doped M-Si—Al—O—N materials” written by J. W. H. vanKrevel, TU Eindhoven 2000, ISBN, 90-386-2711-4

[Patent Literature 1]

JP-A-2002-363554

[Patent Literature 2]

U.S. Pat. No. 6,682,663

[Patent Literature 3]

JP-A-2003-206481

[Patent Literature 4]

JP-A-2002-322474

[Patent Literature 5]

JP-A-2003-321675

[Patent Literature 6]

JP-A-2003-277746

[Patent Literature 7]

JP-A-2004-10786

As conventional art of lighting apparatus, a white light-emitting diodewherein a blue light-emitting diode element and a blue light-absorbingyellow light-emitting phosphor are combined is known and has beenpractically used in various lighting applications. Representativeexamples thereof include “a light-emitting diode” of Japanese Patent No.2900928 (Patent Literature 8), “a light-emitting diode” of JapanesePatent No. 2927279 (Patent Literature 9), “a wavelength-convertingmolding material and a process for producing the same, and alight-emitting element” of Japanese Patent No. 3364229 (PatentLiterature 10), and the like. Phosphors most frequently used in theselight-emitting diode are yttrium.aluminum.garnet-based phosphorsactivated with cerium represented by the general formula:(Y,Gd)₃(Al,Ga)₅ O ₁₂ :Ce ³⁺.

However, there is a problem that the white light-emitting diodecomprising a blue light-emitting diode element and theyttrium.aluminum.garnet-based phosphor has a characteristic of emittinga bluish-white light because of an insufficient red component and hencedeflection is found in color-rendering properties.

Based on such a background, there has been investigated a whitelight-emitting diode wherein a red component which is short in theyttrium.aluminum.garnet-based phosphor is supplemented with another redphosphor by mixing and dispersing two kinds of phosphors. As suchlight-emitting diodes, “a white light-emitting diode” of JP-A-10-163535(Patent Literature 11), “a nitride phosphor and a process for producingthe same” of JP-A-2003-321675 (Patent Literature 5), and the like can beexemplified. However, a problem to be improved regarding color-renderingproperties still remains also in these inventions, and hence it isdesired to develop a light-emitting diode where the problem is solved.The red phosphor described in JP-A-10-163535 (Patent Literature 11)contains cadmium and thus there is a problem of environmental pollution.Although red light emitting phosphors including Ca_(1.97)Si₅N₈:Eu_(0.03)described in JP-A-2003-321675 (Patent Literature 5) as a representativeexample do not contain cadmium but further improvement of their emissionintensities has been desired since luminance of the phosphor is low.

[Patent Literature 8]

Japanese Patent No. 2900928

[Patent Literature 9]

Japanese Patent No. 2927279

[Patent Literature 10]

Japanese Patent No. 3364229

[Patent Literature 11]

JP-A-10-163535

DISCLOSURE OF THE INVENTION

The invention intends to reply such demands and an object thereof is toprovide an inorganic phosphor which emits an orange or red light havinga longer wavelength than that of conventional sialon phosphors activatedwith a rare earth, has a high luminance, and is chemically stable.Furthermore, another object of the invention is to provide a lightingequipment excellent in color-rendering properties, an image display unitexcellent in durability, a pigment, and an ultraviolet absorbent usingsuch a phosphor.

Under such circumstances, the present inventors have conducted precisestudies on phosphors using as a host an inorganic multi-element nitridecrystal phase containing trivalent E Element such as Al in addition todivalent A Element such as Ca and tetravalent D Element such as Si asmain metal elements and have found that a phosphor using an inorganiccrystal phase having a specific composition or a specific crystalstructure as a host emits an orange or red light having a longerwavelength than that of conventional sialon phosphors activated with arare earth and also exhibits a higher luminance than that of the redphosphors hitherto reported containing a nitride or oxynitride as a hostcrystal.

Namely, as a result of extensive studies on inorganic compounds mainlycomposed of nitrides or oxynitrides containing M Element which becomes alight-emitting ion (wherein M Element is one or two or more elementsselected from Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) anddivalent A Element (wherein A Element is one or two or more elementsselected from Mg, Ca, Sr, and Ba), tetravalent D Element (wherein DElement is one or two or more elements selected from Si, Ge, Sn, Ti, Zr,and Hf), trivalent E Element (wherein E Element is one or two or moreelements selected from B, Al, Ga, In, Sc, Y, La, Gd and Lu), and XElement (wherein X Element is one or two or more elements selected fromO, N, and F), they have found that those having a specific compositionregion range and a specific crystal phase form phosphors emitting anorange light having a wavelength of 570 nm or longer or a red lighthaving a wavelength of 600 nm or longer.

Furthermore, they have found that, among the above compositions, a solidsolution crystal phase containing an inorganic compound having the samecrystal structure as that of the CaAlSiN₃ crystal phase as a hostcrystal and incorporated with an optically active element M,particularly Eu as an emission center forms a phosphor emitting anorange or red light having an especially high luminance. Furthermore,they have found that a white light-emitting diode which has a highemission efficiency, is rich in a red component, and exhibits goodcolor-rendering properties can be obtained by using the phosphor.

The host crystal of the phosphor of the invention achieves red-lightemission exhibiting an unprecedented luminance by using themulti-element nitride wherein a trivalent element including Al as arepresentative is used as a main constitutive metal element, quiteunlike the ternary nitrides containing divalent and tetravalent elementshitherto reported including L_(x)M_(y)N_((2/3x+4/3y)) as arepresentative. Moreover, the invention is a novel phosphor using acrystal phase having a composition and crystal structure quite differentfrom the sialons such as M₁₃Si₁₈Al₁₂O₁₈N₃₆, MSi₅Al₂ON₉, and M₃Si₅AlON₁₀(wherein M represents Ca, Ba, Sr, or the like) hitherto reported inPatent Literature 3 and the like and Ca_(1.47)Eu_(0.03)Si₉Al₃N₁₆described in Chapter 11 of Non-Patent Literature 2 as a host.Furthermore, unlike the crystal phase containing Al in an amount ofabout several hundreds of ppm described in Patent Literature 5, it is aphosphor using as a host a crystal phase wherein a trivalent elementincluding Al as a representative is a main constitutive element of thehost crystal.

In general, a phosphor wherein an inorganic host crystal is activatedwith Mn or a rare earth metal as an emission center element M changes anemitting color and luminance depending on an electron state around MElement. For example, in a phosphor containing divalent Eu as theemission center, light emission of blue color, green color, yellowcolor, or red color has been reported by changing the host crystal.Namely, even in the case that the composition is resemble, when thecrystal structure of the host or the atom position in the crystalstructure to which M is incorporated is changed, the emitting color andluminance become quite different and thus the resulting phosphor isregarded as a different one. In the invention, a multi-element nitridecontaining divalent-trivalent-tetravalent elements different fromconventional ternary nitrides containing divalent and tetravalentelements is used as a host crystal and furthermore, a crystal phasehaving a crystal structure quite different from that of the sialoncomposition hitherto reported is used as a host. Thus, the phosphorhaving such a crystal phase as a host has not hitherto been reported. Inaddition, the phosphor containing the composition and crystal structureof the invention as a host exhibits a red light emission havingluminance higher than that of those containing a conventional crystalstructure as a host.

The above CaAlSiN₃ crystal phase itself is a nitride whose formation inthe process of baking an Si₃N₄—AlN—CaO based raw material is confirmedby ZHEN-KUN-HUANG et al. for the purpose of aiming at a heat-resistantmaterial. A process of the formation and a mechanism of the formationare precisely reported in an academic literature (c.f. Non-PatentLiterature 3), which has been published prior to the presentapplication.

[Non-Patent Literature 3]

ZHEN-KUN-HUANG and other two persons, “Journal of Materials ScienceLetters” 1985, vol. 4, pages 255-259

As mentioned above, the CaAlSiN₃ crystal phase itself is confirmed inthe progress of the study of sialons. Also, from the circumstances, thecontent of the report described in the above literature only mentionsheat-resistant properties and the literature does not describe anymatter that an optically active element may be dissolved in the crystalphase and the dissolved crystal phase may be used as a phosphor.Moreover, over the period from that time to the present invention, thereis no investigation to use it as a phosphor. Namely, the importantfindings that a substance obtained by dissolving an optically activeelement in CaAlSiN₃ crystal phase is a novel substance and it is usableas a phosphor capable of being excited with an ultraviolet ray and avisible light and exhibiting an orange or red light emission having ahigh luminance have been first found by the present inventors. As aresult of further extensive studies based on the findings, the inventorshave succeeded in providing a phosphor showing an emission phenomenonwith a high luminance in a specific wavelength region by theconstitutions described in the following (1) to (24). Moreover, theyhave also succeeded in providing a lighting equipment and an imagedisplay unit having excellent characteristics by the constitutionsdescribed in the following (25) to (37) by using the phosphor.Furthermore, by applying the inorganic compound as the phosphor to theconstitutions described in the following (38) to (39), they have alsosucceeded in providing a pigment and an ultraviolet absorbent. Namely,as a result of a series of experiments and studies based on the abovefindings, the invention has succeeded in providing a phosphor emitting alight with a high luminance in a long wavelength region as well as alighting equipment, an image display unit, a pigment, and an ultravioletabsorbent utilizing the phosphor. The constitutions are as described inthe following (1) to (39).

(1) A phosphor comprising an inorganic compound which is a compositioncontaining at least M Element, A Element, D Element, E Element, and XElement (wherein M Element is one or two or more elements selected fromthe group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, andYb, A Element is one or two or more elements selected from the groupconsisting of divalent metal elements other than M Element, D Element isone or two or more elements selected from the group consisting oftetravalent metal elements, E Element is one or two or more elementsselected from the group consisting of trivalent metal elements, and XElement is one or two or more elements selected from the groupconsisting of O, N, and F).

(2) The phosphor according to the above item (1), wherein the inorganiccompound has the same crystal structure as that of CaAlSiN₃.

(3) The phosphor according to the above item (1) or (2), wherein theinorganic compound is represented by the composition formulaM_(a)A_(b)D_(c)E_(d)X_(e) (wherein a+b=1 and M Element is one or two ormore elements selected from the group consisting of Mn, Ce, Pr, Nd, Sm,Eu, Tb, Dy, Ho, Er, Tm, and Yb, A Element is one or two or more elementsselected from the group consisting of divalent metal elements other thanM Element, D Element is one or two or more elements selected from thegroup consisting of tetravalent metal elements, E Element is one or twoor more elements selected from the group consisting of trivalent metalelements, and X Element is one or two or more elements selected from thegroup consisting of O, N, and F), wherein the parameters a, c, d, and esatisfy all the requirements:0.00001≤a≤0.1  (i),0.5≤c≤4  (ii),0.5≤d≤8  (iii),0.8×(2/3+4/3×x+d)≤e  (iv), ande≤1.2×(2/3+4/3×c+d)  (v).

(4) The phosphor according to the above item (3), wherein the parametersc and d satisfy the requirements of 0.5≤c≤1.8 and 0.5≤d≤1.8.

(5) The phosphor according to the above item (3) or (4), wherein theparameters c, d, and e are c=d=1 and e=3.

(6) The phosphor according to any one of the above items (1) to (5),wherein A Element is one or two or more elements selected from the groupconsisting of Mg, Ca, Sr, and Ba, D Element is one or two or moreelements selected from the group consisting of Si, Ge, Sn, Ti, Zr, andHf, and E Element is one or two or more elements selected from the groupconsisting of B, Al, Ga, In, Sc, Y, La, Gd, and Lu.

(7) The phosphor according to any one of the above items (1) to (6),which contains, at least, Eu in M Element, Ca in A Element, Si in DElement, Al in E Element, and N in X Element.

(8) The phosphor according to any one of the above items (1) to (7),wherein the inorganic compound is a CaAlSiN₃ crystal phase or a solidsolution of a CaAlSiN₃ crystal phase.

(9) The phosphor according to any one of the above items (1) to (8),wherein M Element is Eu, A Element is Ca, D Element is Si, E Element isAl, and X Element is N or a mixture of N and O.

(10) The phosphor according to any one of the above items (1) to (9),which contains, at least, Sr in A Element.

(11) The phosphor according to the above item (10), wherein numbers ofatoms of Ca and Sr contained in the inorganic compound satisfy 0.02(number of atoms of Ca)/{(number of atoms of Ca)+(number of atoms ofSr)}<1.

(12) The phosphor according to any one of the above items (1) to (11),which contains, at least, N and O in X.

(13) The phosphor according to the above item (12), wherein numbers ofatoms of O and N contained in the inorganic compound satisfy 0.5≤(numberof atoms of N)/{(number of atoms of N)+(number of atoms of O)}≤1.

(14) The phosphor according to the above item (12) or (13), wherein theinorganic compound is represented byM_(a)A_(b)D_(1−x)E_(1+x)N_(3−x)O_(x) (wherein a+b=1 and 0<x≤0.5).

(15) The phosphor according to any one of the above items (1) to (14),wherein the inorganic compound is a powder having an average particlesize of 0.1 μm to 20 μm and the powder is single crystal particles or anaggregate of single crystals.

(16) The phosphor according to any one of the above items (1) to (15),wherein total of impurity elements of Fe, Co, and Ni contained in theinorganic compound is 500 ppm or less.

(17) A phosphor which is constituted by a mixture of the phosphorcomprising the inorganic compound according to anyone of the above items(1) to (16) and other crystal phase or an amorphous phase and whereinthe content of the phosphor comprising the inorganic compound accordingto any one of the above items (1) to (16) is 20% by weight or more.

(18) The phosphor according to the above item (17), wherein the othercrystal phase or amorphous phase is an inorganic substance havingelectroconductivity.

(19) The phosphor according to the above item (18), wherein theinorganic substance having electroconductivity is an oxide, oxynitride,or nitride containing one or two or more elements selected from thegroup consisting of Zn, Al, Ga, In, and Sn, or a mixture thereof.

(20) The phosphor according to the above item (17), wherein the othercrystal phase or amorphous phase is an inorganic phosphor different fromthe phosphor according to any one of the above items (1) to (16).

(21) The phosphor according to any one of the above items (1) to (20),which emits a fluorescent light having a peak in the range of awavelength of 570 nm to 700 nm by irradiation with an excitation source.

(22) The phosphor according to the above item (21), wherein theexcitation source is an ultraviolet ray or a visible light having awavelength of 100 nm to 600 nm.

(23) The phosphor according to the above item (21), wherein theinorganic compound is a CaAlSiN₃ crystal phase and Eu is dissolved inthe crystal phase, and which emits a fluorescent light having awavelength of 600 nm to 700 nm when irradiated with a light of 100 nm to600 nm.

(24) The phosphor according to the above item (21), wherein theexcitation source is an electron beam or an X-ray.

(25) The phosphor according to any one of the above items (21) to (24),wherein a color emitted at the irradiation with an excitation sourcesatisfies a requirement:0.45≤x≤0.7as a value of (x, y) on the CIE chromaticity coordinates.

(26) A lighting equipment constituted by a light-emitting source and aphosphor, wherein at least the phosphor according to any one of theabove items (1) to (25) is used.

(27) The lighting equipment according to the above item (26), whereinthe light-emitting source is an LED emitting a light having a wavelengthof 330 nm to 500 nm.

(28) The lighting equipment according to the above item (26) or (27),wherein the light-emitting source is an LED emitting a light having awavelength of 330 nm to 420 nm and which emits a white light with mixingred, green, and blue lights by using the phosphor according to any oneof the above items (1) to (25), a blue phosphor having an emission peakat a wavelength of 420 nm to 500 nm with an excitation light of 330 nmto 420 nm, and a green phosphor having an emission peak at a wavelengthof 500 nm to 570 nm with an excitation light of 330 nm to 420 nm.

(29) The lighting equipment according to the above item (26) or (27),wherein the light-emitting source is an LED emitting a light having awavelength of 420 nm to 500 nm and which emits a white light by usingthe phosphor according to any one of the above items (1) to (25) and agreen phosphor having an emission peak at a wavelength of 500 nm to 570nm with an excitation light of 420 nm to 500 nm.

(30) The lighting equipment according to the above item (26) or (27),wherein the emitting source is an LED emitting a light having awavelength of 420 nm to 500 nm and which emits a white light by using aphosphor according to any one of the above items (1) to (25) and ayellow phosphor having an emission peak at a wavelength of 550 nm to 600nm with an excitation light of 420 nm to 500 nm.

(31) The lighting equipment according to the above item (30), whereinthe yellow phosphor is a Ca-asialon in which Eu is dissolved.

(32) An image display unit constituted by an excitation source and aphosphor, wherein at least the phosphor according to any one of theabove items (1) to (25) is used.

(33) The image display unit according to the above item (32), whereinthe excitation source is an LED emitting a light having a wavelength of330 nm to 500 nm.

(34) The image display unit according to the above item (32) or (33),wherein the excitation source is an LED emitting a light having awavelength of 330 nm to 420 nm and which emits a white light with mixingred, green, and blue lights by using the phosphor according to any oneof the above items (1) to (25), a blue phosphor having an emission peakat a wavelength of 420 nm to 500 nm with an excitation light of 330 nmto 420 nm, and a green phosphor having an emission peak at a wavelengthof 500 nm to 570 nm with an excitation light of 330 nm to 420 nm.

(35) The image display unit according to the above item (32) or (33),wherein the emitting source is an LED emitting a light having awavelength of 420 nm to 500 nm and which emits a white light by usingthe phosphor according to any one of the above items (1) to (25) and agreen phosphor having an emission peak at a wavelength of 500 nm to 570nm with an excitation light of 420 nm to 500 nm.

(36) The image display unit according to the above item (32) or (33),wherein the emitting source is an LED emitting a light having awavelength of 420 nm to 500 nm and which emits a white light by usingthe phosphor according to any one of the above items (1) to (25) and ayellow phosphor having an emission peak at a wavelength of 550 nm to 600nm with an excitation light of 420 nm to 500 nm.

(37) The image display unit according to the above item (36), whereinthe yellow phosphor is a Ca-asialon in which Eu is dissolved.

(38) The image display unit according to the above items (32) to (37),wherein the image display unit is any of a vacuum fluorescent display(VFD), a field emission display (FED), a plasma display panel (PDP), anda cathode-ray tube (CRT).

(39) A pigment comprising the inorganic compound according to any one ofthe above items (1) to (25).

(40) An ultraviolet absorbent comprising the inorganic compoundaccording to any one of the above items (1) to (25).

The phosphor of the invention contains a multi-element nitridecontaining a divalent element, a trivalent element, and a tetravalentelement, particularly a crystal phase represented by CaAlSiN₃, anothercrystal phase having the same crystal structure as it, or a solidsolution of these crystal phases as amain component and thereby exhibitslight emission at a longer wavelength than that in the cases ofconventional sialon and oxynitride phosphors, so that the phosphor ofthe invention is excellent as an orange or red phosphor. Even whenexposed to an excitation source, the phosphor does not exhibit decreaseof luminance and thus provides a useful phosphor which is suitablyemployed in VFD, FED, PDP, CRT, white LED, and the like. Moreover, amongthe phosphors, since the host of a specific inorganic compound has a redcolor and the compound absorbs an ultraviolet ray, it is suitable as ared pigment and an ultraviolet absorbent.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1-1 is an X-ray diffraction chart of CaAlSiN₃.

FIG. 1-2 is an X-ray diffraction chart of CaAlSiN₃ activated with Eu(Example 1).

FIG. 2 is a drawing illustrating a crystal structure model of CaAlSiN₃.

FIG. 3 is a drawing illustrating a crystal structure model of Si₂N₂Ohaving a similar structure to the CaAlSiN₃ crystal phase.

FIG. 4 is a drawing illustrating emission spectra of phosphors (Examples1 to 7).

FIG. 5 is a drawing illustrating excitation spectra of phosphors(Examples 1 to 7).

FIG. 6 is a drawing illustrating emission spectra of phosphors (Examples8 to 11).

FIG. 7 is a drawing illustrating excitation spectra of phosphors(Examples 8 to 11).

FIG. 8 is a drawing illustrating emission spectra of phosphors (Examples12 to 15).

FIG. 9 is a drawing illustrating excitation spectra of phosphors(Examples 12 to 15).

FIG. 10 is a drawing illustrating emission spectra of phosphors(Examples 16 to 25).

FIG. 11 is a drawing illustrating excitation spectra of phosphors(Examples 16 to 25).

FIG. 12 is a drawing illustrating emission spectra of phosphors(Examples 26 to 30).

FIG. 13 is a drawing illustrating excitation spectra of phosphors(Examples 26 to 30).

FIG. 14 is a schematic drawing of the lighting equipment (LED lightingequipment) according to the invention.

FIG. 15 is a schematic drawing of the image display unit (plasma displaypanel) according to the invention.

In this connection, with regard to the symbols in the figures, 1represents a mixture of a red phosphor of the invention and a yellowphosphor or a mixture of a red phosphor of the invention, a bluephosphor, and a green phosphor, 2 represents an LED chip, 3 and 4represent electroconductive terminals, 5 represents a wire bond, 6represents a resin layer, 7 represents a container, 8 represents a redphosphor of the invention, 9 represents a green phosphor, 10 representsa blue phosphor, 11, 12, and 13 represent ultraviolet ray-emittingcells, 14, 15, 16, and 17 represent electrodes, 18 and 19 representdielectric layers, 20 represents a protective layer, and 21 and 22represent glass substrates.

BEST MODE FOR CARRYING OUT THE INVENTION

The following will describe the present invention in detail withreference to Examples of the invention.

The phosphor of the invention comprises an inorganic compound which is(1) a composition containing at least M Element, A Element, D Element, EElement, and X Element (wherein M Element is one or two or more elementsselected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy,Ho, Er, Tm, and Yb, A Element is one or two or more elements selectedfrom the group consisting of divalent metal elements other than MElement, D Element is one or two or more elements selected from thegroup consisting of tetravalent metal elements, E Element is one or twoor more elements selected from the group consisting of trivalent metalelements, and X Element is one or two or more elements selected from thegroup consisting of O, N, and F) and is (2) (a) a crystal phaserepresented by the chemical formula CaAlSiN₃, (b) another crystal phasehaving the same crystal structure as that of the crystal phase, or (c) asolid solution of these crystal phases (hereinafter, these crystalphases are collectively referred to as “a CaAlSiN₃ family crystalphase”). Such a phosphor of the invention shows a particularly highluminance.

M Element is one or two or more elements selected from the groupconsisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. MElement is preferably one or two or more elements selected from thegroup consisting of Mn, Ce, Sm, Eu, Tb, Dy, Er, and Yb. M Element morepreferably contains Eu and is still more preferably Eu.

A Element is one or two or more elements selected from the groupconsisting of divalent metal elements other than M Element.Particularly, A Element is preferably one or two or more elementsselected from the group consisting of Mg, Ca, Sr, and Ba and is morepreferably Ca.

D Element is one or two or more elements selected from the groupconsisting of tetravalent metal elements. Particularly, D Element ispreferably one or two or more elements selected from the groupconsisting of Si, Ge, Sn, Ti, Zr, and Hf and is more preferably Si.

E Element is one or two or more elements selected from the groupconsisting of trivalent metal elements. Particularly, E Element is oneor two or more elements selected from the group consisting of B, Al, Ga,In, Sc, Y, La, Gd, and Lu and is more preferably Al.

X Element is one or two or more elements selected from the groupconsisting of O, N, and F. Particularly, X Element is preferablycomposed of N or N and O.

The composition is represented by the composition formulaM_(a)A_(b)D_(c)E_(d)X_(e). A composition formula is a ratio of numbersof the atoms constituting the substance and one obtained by multiplyinga, b, c, d, and e by an arbitrary number has also the same composition.Therefore, in the invention, the following requirements are determinedto the one obtained by recalculation for a, b, c, d, and e so as to bea+b=1.

In the invention, the values of a, c, d, and e are selected from thevalues satisfying all the following requirements:0.00001≤a≤0.1  (i)0.5≤c≤4  (ii)0.5≤d≤8  (iii)0.8×(2/3+4/3×c+d)≤e  (iv)e≤1.2×(2/3+4/3×c+d)  (v).

a represents an adding amount of M Element which becomes an emissioncenter and the ratio a of numbers of atoms M and (M+A) (whereina=M/(M+A)) in a phosphor is suitably from 0.00001 to 0.1. When a Valueis less than 0.00001, the number of M becoming an emmision center issmall and hence emission luminance decreases. When a Value is largerthan 0.1, concentration quenching occurs owing to interference between Mions, so that luminance decreases.

In particular, in the case that M is Eu, a Value is preferably from0.002 to 0.03 owing to high emission luminance.

c Value is the content of D Element such as Si and is an amountrepresented by 0.5≤c≤4. The value is preferably 0.5≤c≤1.8, morepreferably c=1. When c Value is less than 0.5 and when the value islarger than 4, emission luminance decreases. In the range of 0.5≤c≤1.8,emission luminance is high and particularly, emission luminance isespecially high at c=1. The reason therefor is that the ratio offormation of the CaAlSiN₃ family crystal phase to be described belowincreases.

d Value is the content of E Element such as Al and is an amountrepresented by 0.5≤d≤8. The value is preferably 0.5≤d≤1.8, morepreferably d=1. When d Value is less than 0.5 and when the value islarger than 8, emission luminance decreases. In the range of 0.5≤d≤1.8,emission luminance is high and particularly, emission luminance isespecially high at d=1. The reason therefor is that the ratio offormation of the CaAlSiN₃ family crystal phase to be described belowincreases.

e Value is the content of X Element such as N and is an amountrepresented by from 0.8×(2/3+4/3×c+d) to 1.2×(2/3+4/3×c+d). Morepreferably, e=3. The reason therefor is that the ratio of formation ofthe CaAlSiN₃ family crystal phase to be described below increases. Whene Value is out of the range, emission luminance decreases.

Among the above compositions, compositions exhibiting a high emissionluminance are those which contain, at least, Eu in M Element, Ca in AElement, Si in D Element, Al in E Element, and N in X Element. Inparticular, the composition are those wherein M Element is Eu, A Elementis Ca, D Element is Si, E Element is Al, and X Element is N or a mixtureof N and O.

The above CaAlSiN₃ crystal phase is an orthorhombic system and is asubstance characterized by a crystal phase having lattice constants ofa=9.8007(4) Å, b=5.6497(2) Å, and c=5.0627(2) Å and having indices ofcrystal plane described in the chart of FIG. 1-1 and Table 4 in X-raydiffraction.

According to the crystal structure analysis of the CaAlSiN₃ crystalphase conducted by the inventors, the present crystal phase belongs toCmc2₁ (36th space group of International Tables for Crystallography) andoccupies an atomic coordinate position shown in Table 5. In thisconnection, the space group is determined by convergent beam electrondiffraction and the atomic coordinate is determined by Rietveld analysisof X-ray diffraction results.

The crystal phase has a structure shown in FIG. 2 and has a similarskeleton to the Si₂N₂O crystal phase (mineral name: sinoite) shown inFIG. 3. Namely, the crystal phase is a crystal phase wherein theposition of Si in the Si₂N₂O crystal phase is occupied by Si and Al andthe positions of N and O are occupied by N, and Ca is incorporated as aninterstitial element into a space of the skeleton formed by Si—N—O, andhas a structure where the atomic coordinates are changed to thepositions shown in Table 5 with the replacement of the elements. Si andAl occupy the Si position in the Si₂N₂O crystal phase in an irregularlydistributed (disordered) state. Thus, this structure is named as asinoite-type sialon structure.

The inorganic compound having the same crystal structure as CaAlSiN₃shown in the invention means the inorganic compound which is a CaAlSiN₃family crystal phase mentioned above. The inorganic compound having thesame crystal structure as CaAlSiN₃ includes those having latticeconstants changed by the replacement of the constitutive element(s) withother element(s) in addition to the substances showing the samediffraction as the results of X-ray diffraction of CaAlSiN₃. Forexample, a CaAlSiN₃ crystal phase, a solid solution of the CaAlSiN₃crystal phase, and the like may be mentioned. Herein, one wherein theconstitutive element(s) are replaced with other element(s) means acrystal phase wherein, in the case of the CaAlSiN₃ crystal phase, forexample, Ca in the crystal phase is replaced with M Element (wherein MElement is one or two or more elements selected from the groupconsisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) and/orM Element and one or two or more elements selected from the groupconsisting of divalent metal elements other than Ca, preferably thegroup consisting of Mg, Sr, and Ba, Si is replaced with one or two ormore elements selected from the group consisting of tetravalent metalelements other than Si, preferably the group consisting of Ge, Sn, Ti,Zr, and Hf, Al is replaced with one or two or more elements selectedfrom the group consisting of trivalent metal elements other than Al,preferably the group consisting of B, Ga, In, Sc, Y, La, Gd, and Lu, andN is replaced with one or two or more elements selected from the groupconsisting of O and F. In this connection, the CaAlSiN₃ family crystalphase of the invention can be identified by X-ray diffraction orneutron-ray diffraction.

The CaAlSiN₃ family crystal phase is changed in lattice constants by thereplacement of Ca, Si, Al, or N as the constitutive components withother element(s) or the dissolution of a metal element such as Eu butthe atomic position determined by the crystal structure, the siteoccupied by the atom, and its coordinate is changed to not so largeextent that the chemical bond between skeletal atoms is cleaved. In theinvention, in the case that the lengths of chemical bonds of Al—N andSi—N (distance between adjacent atoms) calculated from the latticeconstants and atomic coordinates determined by Rietveld analysis of theresults of X-ray diffraction and neutron-ray diffraction with the spacegroup of Cmc2₁ are within ±15% as compared with the length of thechemical bond calculated from the lattice constants and atomiccoordinates of CaAlSiN₃ shown in Table 5, it is defined that the crystalphase has the same crystal structure. In this manner, a crystal phase isjudged whether it is a CaAlSiN₃ family crystal phase or not. Thisjudging standard is based on the fact that, when the length of thechemical bond changes beyond ±15%, the chemical bond is cleaved andanother crystal phase is formed.

Furthermore, when the dissolved amount is small, the following methodmay be a convenient judging method of a CaAlSiN₃ family crystal phase.When the lattice constants calculated from the results of X-raydiffraction measured on a new substance and the peak position (2θ) ofdiffraction calculated using the indices of crystal plane in Table 4 arecoincident with regard to main peaks, the crystal structures can beidentified to be the same. As the main peaks, it is appropriate toconduct the judgment on about ten peaks exhibiting strong diffractionintensity. In that sense, Table 4 is a standard for identifying theCaAlSiN₃ family crystal phase and thus is of importance. Moreover, withregard to the crystal structure of the CaAlSiN₃ crystal phase, anapproximate structure can be defined also using another crystal systemsuch as a monoclinic system or a hexagonal system. In that case, theexpression may be one using different space group, lattice constants,and indices of crystal plane but the results of X-ray diffraction arenot changed and the identification method and identification resultsusing the same are identical thereto. Therefore, in the invention, X-raydiffraction is analyzed as an orthorhombic system. The identificationmethod of substances based on Table 4 will be specifically described inExample 1 to be described below and only a schematic explanation isconducted here.

A phosphor is obtained by activating a CaAlSiN₃ family crystal phasewith M Element (wherein M Element is one or two or more elementsselected from the group consisting of Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy,Ho, Er, Tm, and Yb). The phosphor having a particularly high luminanceamong the CaAlSiN₃ family crystal phases is a phosphor containing as ahost a CaAlSiN₃ crystal phase using a combination that A is Ca, D is Si,E is Al, and X is N.

A phosphor using Ca_(x)Sr_(1−x)AlSiN₃ (wherein 0.02≤x≤1) crystal phasewhich is a crystal phase obtained by replacing part of Ca with Sr or itssolid solution as host crystals, i.e., a phosphor wherein numbers ofatoms of Ca and Sr contained in the inorganic compound satisfy 0.02(number of atoms of Ca)/{(number of atoms of Ca)+(number of atoms ofSr)}<1, becomes a phosphor exhibiting a shorter wavelength than that ofthe phosphor using as a host a CaAlSiN₃ crystal phase having acomposition of the range.

The phosphor using as a host an inorganic compound containing nitrogenand oxygen is excellent in durability in a high-temperature air. In thiscase, durability at a high temperature is particularly excellent at thecomposition where numbers of atoms of O and N contained in the inorganiccompound satisfy 0.5≤(number of atoms of N)/{(number of atoms ofN)+(number of atoms of O))≤1.

In the case that the inorganic compound containing nitrogen and oxygenis used as a host, since the ratio of formation of the CaAlSiN₃ familycrystal phase increases at the composition represented byM_(a)A_(b)D_(1−x)E_(1+x)N_(3−x)O_(x) (wherein a+b=1 and 0<x≤0.5),emission luminance is high. This is because trivalent N is replaced withdivalent O by the number of the atom the same as the number of thetetravalent D Element replaced with trivalent E Element in thecomposition and hence charge neutrality is maintained, so that a stableCaAlSiN₃ family crystal phase is formed.

In the case that the phosphor comprising the inorganic compound havingthe same crystal structure as CaAlSiN₃ of the invention is used as apowder, the average particle size of the inorganic compound ispreferably from 0.1 μm to 20 μm in view of dispersibility into the resinand fluidity of the powder. Moreover, the powder is single crystalparticles or an aggregate of single crystals but emission luminance isfurther improved by using single crystal particles having an averageparticle size of 0.1 μm to 20 μm.

In order to obtain a phosphor exhibiting a high emission luminance, theamount of impurities contained in the inorganic compound is preferablyas small as possible. In particular, since the contamination of a largeamount of Fe, Co, and Ni impurity elements inhibits light emission, itis suitable that raw powders are selected and the synthetic steps arecontrolled so that the total of these elements becomes not more than 500ppm.

In the invention, from the viewpoint of fluorescence emission, it isdesirable that the nitride contain the CaAlSiN₃ family crystal phase asa constitutive component of the nitride in high purity and as much aspossible, and is possibly composed of a single phase, but it may becomposed of a mixture thereof with the other crystal phases or anamorphous phase within the range where the characteristics do notdecrease. In this case, it is desirable that the content of the CaAlSiN₃family crystal phase is 50% by weight or more in order to obtain a highluminance. Further preferably, when the content is 20% by weight ormore, luminance is remarkably improved. In the invention, the range as amain component is a content of the CaAlSiN₃ family crystal phase of atleast 20% by weight or more. The ratio of content of the CaAlSiN₃ familycrystal phase can be determined from the ratio of the intensity of thestrongest peaks in respective phases of the CaAlSiN₃ family crystalphase and the other crystal phases through the measurement of X-raydiffraction.

In the case that the phosphor of the invention is used for applicationsexcited with an electron beam, electroconductivity can be imparted tothe phosphor by mixing it with an inorganic substance havingelectroconductivity. As the inorganic substance havingelectroconductivity, there may be mentioned oxides, oxynitrides, ornitrides containing one or two or more elements selected from the groupconsisting of Zn, Al, Ga, In, and Sn, or mixtures thereof.

The phosphor of the invention can emit a red light by the combination ofa specific host crystal and an activating element but, in the case thatmixing with the other colors such as yellow color, green color, and bluecolor is necessary, it is possible to mix inorganic phosphors emittinglights of these colors according to necessity.

The phosphors of the invention exhibit different excitation spectra andfluorescent spectra depending on the composition and hence can be set atthose having various emission spectra by suitably selecting andcombining them. The embodiment may be appropriately set at a requiredspectrum based on the application. Particularly, one wherein Eu is addedto the CaAlSiN₃ crystal phase in a composition of 0.0001 (number ofatoms of Eu)/{(number of atoms of Eu)+(number of atoms of Ca)}≤0.1exhibits emission of a light having a peak in the range of a wavelengthof 600 nm to 700 nm when excited with a light having a wavelength in therange of 100 nm to 600 nm, preferably 200 nm to 600 nm, and exhibitsexcellent emission characteristics as red fluorescence.

The phosphors of the invention obtained as above are characterized inthat they have a wide excitation range of from an electron beam or anX-ray and an ultraviolet ray to a visible light, i.e., ultraviolet raysor visible lights having wavelengths from 100 nm to 600 nm, emit anorange to red light of 570 nm or longer, and particularly exhibit redcolor of 600 nm to 700 nm at a specific composition, and they exhibit ared light ranging 0.45≤x≤0.7 in terms of the value of (x, y) on CIEchromaticity coordinates, as compared with conventional oxide phosphorsand existing sialon phophors. Owing to the above emissioncharacteristics, they are suitable for a lighting equipment, an imagedisplay unit, a pigment, and an ultraviolet absorbent. In addition,since they are not degraded even when exposed to a high temperature,they are excellent in heat resistance and also excellent in long-termstability under an oxidizing atmosphere and under a moist environment.

The phosphors of the invention do not limit the production process but aphosphor exhibiting a high luminance can be produced by the followingprocess.

A high-luminance phosphor is obtained by baking a raw material mixture,which is a mixture of metal compounds and may constitute a compositionrepresented by M, A, D, E, and X by baking the mixture, at a temperaturerange of 1200° C. to 2200° C. in an inert atmosphere containingnitrogen.

In the case of synthesizing CaAlSiN₃ activated with Eu, it is suitableto use a powder mixture of europium nitride or europium oxide, calciumnitride, silicon nitride, and aluminum nitride as a starting material.

Moreover, in the case of synthesizing a composition containingstrontium, incorporation of strontium nitride in addition to the aboveaffords a stable (Ca, Sr)AlSiN₃ crystal phase wherein part of thecalcium atoms in the crystal phase is replaced with strontium, whereby ahigh-luminance phosphor is obtained.

In the case of synthesizing a phosphor using as a host CaAlSi (O,N)₃ andactivated with Eu, wherein part of the nitrogen atom in the crystalphase is replaced with oxygen, a starting material of a mixture ofeuropium nitride, calcium nitride, silicon nitride, and aluminum nitrideis preferable in the composition of a small oxygen content since thematerial has a high reactivity and the synthesis in high yields ispossible. In this case, as oxygen, oxygen impurity contained in the rawmaterial powders of europium nitride, calcium nitride, silicon nitride,and aluminum nitride is used.

In the case of synthesizing a phosphor of a large oxygen content usingCaAlSi(O,N)₃ activated with Eu as a host, when a mixture of either ofeuropium nitride or europium oxide or a mixture thereof, anyone ofcalcium nitride, calcium oxide, or calcium carbonate or a mixturethereof, silicon nitride, and aluminum nitride or a mixture of aluminumnitride and aluminum oxide is used as a starting material, the materialhas a high reactivity and the synthesis in high yields is possible.

It is appropriate that the above mixed powder of the metal compounds isbaked in a state that a volume filling rate is maintained to 40% orless. In this connection, the volume filling rate can be determinedaccording to (bulk density of mixed powder)/(theoretical density ofmixed powder)×100 [%]. As a vessel, a boron nitride sintered article issuitable because of low reactivity with the metal compounds.

The reason why the powder is baked in a state that a volume filling rateis maintained to 40% or less is that baking in the state that a freespace is present around the starting powder enables synthesis of acrystal phase having little surface defect since the CaAlSiN₃ familycrystal phase as a reaction product grows in a free space and hence thecontact of the crystal phases themselves decreases.

Next, a phosphor is synthesized by baking the resulting mixture of themetal compounds in a temperature range of 1200° C. to 2200° C. in aninert atmosphere containing nitrogen. Since the baking is conducted at ahigh temperature and the baking atmosphere is an inert atmospherecontaining nitrogen, the furnace for use in the baking is ametal-resistor resistive heating type one or a graphite resistiveheating type one and an electric furnace using carbon as a material fora high-temperature part of the furnace is suitable. As the method of thebaking, a sintering method of applying no mechanical pressureexternally, such as an atmospheric sintering method or a gas pressuresintering method is preferred since baking is conducted while the volumefilling rate is maintained at 40% or less.

In the case that the powder aggregate obtained by the baking is stronglyadhered, it is pulverized by means of a pulverizing machine usually usedindustrially, such as a ball mill or a jet mill and the like. Thepulverization is conducted until the average particle size reaches 20 μmor less. Particularly preferred is an average particle size of 0.1 μm to5 μm. When the average particle size exceeds 20 μm, fluidity of thepowder and dispersibility thereof into resins become worse and emissionintensity becomes uneven from part to part at the time when an emissionapparatus is formed in combination with a light-emitting element. Whenthe size becomes 0.1 μm or less, the amount of defects on the surface ofa phosphor powder becomes large and hence emission intensity decreasesin some phosphor compositions.

Of the phosphors of the invention, the phosphors using the inorganiccompound containing nitrogen and oxygen as a host can be also producedby the following process.

It is a process wherein oxygen is allowed to exist in the raw materialto be baked so that the ratio (percentage) of mol number of oxygen tototal mol number of nitrogen and oxygen in the raw material to be baked(hereinafter referred to as an “oxygen existing ratio in a rawmaterial”) becomes from 1% to 20% in a state of a bulk density of 0.05g/cm³ to 1 g/cm³ at a baking temperature of 1200° C. to 1750° C. at thetime when a starting mixed powder containing an elementary substanceand/or compound of M Element, a nitride of A Element, a nitride of DElement, and a nitride of E Element is baked.

The oxygen existing ratio in a raw material means a ratio (percentage)of mol number of oxygen to total mol number of nitrogen and oxygen inthe raw material to be baked at baking and the nitrogen in the rawmaterial to be baked is nitrogen derived from the raw powder, while theoxygen includes oxygen to be incorporated from the baking atmosphereinto the material to be baked at baking in addition to the oxygencontained in the raw powder beforehand. The oxygen existing ratio in araw material can be determined by the measurement using an oxygennitrogen analyzer. The oxygen existing ratio in a raw material ispreferably from 2% to 15%.

The method of allowing oxygen to exist in such an oxygen existing ratioin a raw material at baking includes:

(1) a method of using raw nitrides containing a desired concentration ofoxygen as raw materials to be baked,

(2) a method of allowing raw nitrides to contain a desired concentrationof oxygen by heating the raw nitrides beforehand under anoxygen-containing atmosphere,

(3) a method of mixing a raw nitride powder with an oxygen-containingcompound powder to form a raw material to be baked,

(4) a method of introducing oxygen into the raw material to be baked bycontaminating oxygen in the baking atmosphere at baking of raw nitridesand oxidizing the raw nitrides at baking, and the like. In order toproduce a high-luminance phosphor industrially stably, preferred is (1)the method of using raw nitrides containing a desired concentration ofoxygen as raw materials to be baked or (3) the method of mixing a rawnitride powder with an oxygen-containing compound powder to form a rawmaterial to be baked. In particular, more preferred is a method of usingraw nitrides containing a desired concentration of oxygen as rawmaterials to be baked and also mixing the raw nitride powder with anoxygen-containing compound powder to form a raw material to be used,which is a combination of the above methods (1) and (3).

In this case, the oxygen-containing compound powder is selected fromsubstances which form metal oxides at baking. As these substances, usecan be made of oxides, inorganic acid salts such as nitrates, sulfates,and carbonates of respective metals, i.e., metals constituting the rawnitrides, organic acid salts such as oxalates and acetates thereof,oxygen-containing organometallic compounds, and the like, of respectivemetals, i.e., metals constituting the raw nitrides. However, from theviewpoints that oxygen concentration is easily controlled andassociation of impurity gases into the baking atmosphere can besuppressed at a low level, it is preferred to use metal oxides.

The oxygen existing ratio in raw material can be easily determined byconducting chemical analysis of all the raw materials. In particular,the ratio of nitrogen to oxygen can be determined by analyzingconcentrations of nitrogen and oxygen.

The elementary substance and/or compound of M Element to be used as araw material may be any substance as far as M Element is incorporatedinto a host crystal of the phosphor at a high temperature, includingmetals (elementary substances), oxides, nitrides, sulfides, halides,hydrides of M Element and also inorganic acid salts such as nitrates,sulfates, and carbonates, organic acid salts such as oxalates andacetates, organometallic compounds, and the like, and there is nolimitation in its kind. However, from the viewpoint of good reactivitywith other nitride materials, metals, oxides, nitrides, and halides of MElement are preferred and oxides are particularly preferred since theraw materials are available at a low cost and the temperature forphosphor synthesis can be lowered.

In the case of using at least Eu as M Element, use can be made of one ortwo or more of Eu metal containing Eu as a constitutive element,europium oxide such as EuO and Eu₂O₃, and various compounds such as EuN,EuH₃, Eu₂S₃, EuF₂, EuF₃, EuCl₂, EuCl₃,Eu(NO₃)₃/EU₂(SO₄)₃/EU₂(CO₃)₃/Eu(C₂O₄)₃, Eu(O-i-C₃H₇)₃, but Eu halidessuch as EuF₂, EuF₃, EuCl₂, and EuCl₃ are preferred since they have aneffect of accelerating crystal growth. Moreover, Eu₂O₃ and Eu metal arealso preferred since a phosphor having excellent characteristics can besynthesized from them. Of these, Eu₂O₃ is particularly preferred, whichis cheap in a raw material cost, has little deliquescency, and enablessynthesis of a high-luminance phosphor at a relatively low temperature.

As raw materials for elements other than M Element, i.e., raw materialsfor A, D, and E Elements, nitrides thereof are usually used. Examples ofnitrides of A Element include one or two or more of Mg₃N₂, Ca₃N₂, Sr₃N₂,Ba₃N₂, Zn₃N₂, and the like, examples of nitrides of D Element includeone or two or more of Si₃N₄, Ge₃N₄, Sn₃N₄, Ti₃N₄, Zr₃N₄, Hf₃N₄, and thelike, and examples of nitrides of E Element include one or two or moreof AlN, GaN, InN, ScN, and the like. The use of powders thereof ispreferred since a phosphor having excellent emission characteristics canbe produced.

In particular, the use, as raw materials of A Element, of a highlyactive and highly reactive nitride material having mol number of oxygenof 1% to 20% relative to the total mol number of nitrogen and oxygenremarkably accelerates the solid phase reaction between the raw mixedpowder of nitrides and, as a result, it becomes possible to lower thebaking temperature and atmosphere gas pressure at baking withoutsubjecting the raw mixed powder to compression molding. For the samereason, it is preferred to use, as a raw material of A Element, anitride material particularly having mol number of oxygen of 2% to 15%relative to the total mol number of nitrogen and oxygen.

When the bulk density of the raw mixed powder is too small, the solidphase reaction is difficult to proceed owing to small contact areabetween the powdery raw materials and hence an impurity phase whichcannot lead to synthesis of a preferred phosphor may remain in a largeamount. On the other hand, when the bulk density is too large, theresulting phosphor may become a hard sintered one, which not onlyrequires a long-term pulverization step after baking but also tends tolower luminance of the phosphor. Therefore, the bulk density ispreferably from 0.15 g/cm³ to 0.8 g/cm³.

When the baking temperature of the raw mixed powder is too low, thesolid phase reaction is difficult to proceed and the aimed phosphorcannot be synthesized. On the other hand, when it is too high, not onlyunproductive baking energy is consumed but also evaporation of nitrogenfrom the starting material and the produced substance increases andhence there is a tendency that the aimed phosphor cannot be producedunless the pressure of nitrogen which constitutes part of atmosphere gasis increased to a very high pressure. Therefore, the baking temperatureis preferably from 1300° C. to 1700° C. The baking atmosphere of the rawmixed powder is in principle an inert atmosphere or a reductiveatmosphere but the use of an atmosphere containing a minute amount ofoxygen wherein the oxygen concentration is in the range of 0.1 to 1 ppmis preferred since it becomes possible to synthesize a phosphor at arelatively low temperature.

Moreover, the pressure of atmosphere gas at baking is usually 20 atm (2MPa) or lower. A high-temperature baking equipment comprising a strongheat-resistant vessel is required for a pressure exceeding 20 atm andhence the cost necessary for baking becomes high, so that the pressureof the atmosphere gas is preferably 10 atm (1 MPa) or lower. In order toprevent contamination of oxygen in the air, the pressure is preferablyslight higher than 1 atm (0.1 MPa). In the case that air-tightness ofthe baking furnace is wrong, when the pressure is 1 atm (0.1 MPa) orlower, a lot of oxygen contaminates the atmosphere gas and hence it isdifficult to obtain a phosphor having excellent characteristics.

Furthermore, the holding time at the maximum temperature at baking isusually from 1 minute to 100 hours. When the holding time is too short,the solid phase reaction between raw mixed powders does not sufficientlyproceed and an aimed phosphor cannot be obtained. When the holding timeis too long, not only unproductive baking energy is consumed but alsonitrogen is eliminated from the surface of the phosphor and thefluorescence characteristics deteriorate. For the same reasons, theholding time is preferably from 10 minutes to 24 hours.

As explained in the above, the CaAlSiN₃ family crystal phase phosphor ofthe invention exhibits a higher luminance than that of conventionalsialon phosphors and, since decrease in luminance of the phosphor issmall when it is exposed to an excitation source, it is a phosphorsuitable for VFD, FED, PDP, CRT, white LED, and the like.

The lighting equipment of the invention is constituted by the use of atleast a light-emitting source and the phosphor of the invention. As thelighting equipment, there may be mentioned an LED lighting equipment, afluorescent lamp, and the like. The LED lighting equipment can beproduced by known methods as described in JP-A-5-152609, JP-A-7-99345,Japanese Patent No. 2927279, and so forth with the phosphor of theinvention. In this case, the light-emitting source is desirably oneemitting a light having a wavelength of 330 to 500 nm, and particularlypreferred is an ultraviolet (or violet) LED light-emitting element of330 to 420 nm or a blue LED light-emitting element of 420 to 500 nm.

As these light-emitting elements, there exist an element comprising anitride semiconductor such as GaN or InGaN and the like and, byadjusting the composition, it may be employed as a light-emitting sourcewhich emits a light having a predetermined wavelength.

In the lighting equipment, in addition to the method of using thephosphor of the invention solely, by the combined use thereof with aphosphor having other emission characteristics, a lighting equipmentemitting a desired color can be constituted. As one example, there is acombination of an ultraviolet LED light-emitting element of 330 to 420nm with a blue phosphor excited at the wavelength and having an emissionpeak at a wavelength of 420 nm to 500 nm, a green phosphor excited atthe wavelength of 330 to 420 nm and having an emission peak at awavelength of 500 nm to 570 nm, and the phosphor of the invention. Theremay be mentioned BaMgAl₁₀O₁₇:Eu as the blue phosphor andBaMgAl₁₀O₁₇:Eu,Mn as the green phosphor. In this constitution, when thephosphors are irradiated with an ultraviolet ray emitted by the LED,red, green, and blue lights are emitted and a white lighting equipmentis formed by mixing the lights.

As an alternative method, there is a combination of a blue LEDlight-emitting element of 420 to 500 nm with a yellow phosphor excitedat the wavelength and having an emission peak at a wavelength of 550 nmto 600 nm and the phosphor of the invention. As such a yellow phosphor,there may be mentioned (Y, Gd)₂(Al, Ga)₅O₁₂:Ce described in JapanesePatent No. 2927279 and α-sialon:Eu described in JP-A-2002-363554. Ofthese, a Ca-α-sialon in which Eu is dissolved is preferred owing to highemission luminance. In this constitution, when the phosphors areirradiated with a blue light emitted by the LED, two lights having redand yellow colors are emitted and the lights are mixed with the bluelight of LED itself to form a lighting equipment exhibiting a whitecolor or a reddish lamp color.

As another method, there is a combination of a blue LED light-emittingelement of 420 to 500 nm with a green phosphor excited at the wavelengthand having an emission peak at a wavelength of 500 nm to 570 nm and thephosphor of the invention. As such a green phosphor, there may bementioned Y₂Al₅O₁₂:Ce. In this constitution, when the phosphors areirradiated with a blue light emitted by the LED, two lights having redand green colors are emitted and the lights are mixed with the bluelight of LED itself to form a white lighting equipment.

The image display unit of the invention is constituted by at least anexcitation source and the phosphor of the invention and includes avacuum fluorescent display (VFD), a field emission display (FED), aplasma display panel (PDP), a cathode ray tube (CRT), and the like. Thephosphor of the invention is confirmed to emit a light by excitationwith a vacuum ultraviolet ray of 100 to 190 nm, an ultraviolet ray of190 to 380 nm, an electron beam, or the like. Thus, by the combinationof any of these excitation sources and the phosphor of the invention,the image display unit as above can be constituted.

Since the specific inorganic compound of the invention has a red objectcolor, it can be used as a red pigment or a red fluorescent pigment.When the inorganic compound of the invention is irradiated withillumination of sunlight, fluorescent lamp, or the like, a red objectcolor is observed and the compound is suitable as an inorganic pigmentowing to good coloring and no deterioration over a long period of time.Therefore, there is an advantage that the coloring does not decreaseover a long period of time when it is used in coatings, inks, colors,glazes, colorants added to plastic products or the like. The nitride ofthe invention absorbs ultraviolet rays and hence is suitable as anultraviolet absorbent. Therefore, when the nitride is used as a coatingor applied on the surface of plastic products or kneaded into theproducts, the effect of shielding ultraviolet rays is high and thus theeffect of protecting the products from ultraviolet degradation is high.

EXAMPLES

The following will describe the invention further in detail withreference to the following Examples but they are disclosed only for thepurpose of easy understanding of the invention and the invention is notlimited to these Examples.

Example 1

As raw powders were used a silicon nitride powder having an averageparticle size of 0.5 μm, an oxygen content of 0.93% by weight, and ana-type content of 92%, an aluminum nitride powder having a specificsurface area of 3.3 m²/g and an oxygen content of 0.79%, a calciumnitride powder, and europium nitride synthesized by nitriding metaleuropium in ammonia.

In order to obtain a compound represented by the composition formula:Eu_(0.008)Ca_(0.992)AlSiN₃ (Table 1 shows parameters for designedcomposition, Table 2 shows designed composition (% by weight), and Table3 shows a mixing composition of a raw powder), the silicon nitridepowder, the aluminum nitride powder, the calcium nitride powder, and theeuropium nitride powder were weighed so as to be 33.8578% by weight,29.6814% by weight, 35.4993% by weight, and 0.96147% by weight,respectively, followed by 30 minutes of mixing by means of an agatemortar and pestle. Thereafter, the resulting mixture was allowed to fallfreely into a crucible made of boron nitride through a sieve of 500 μmto fill the crucible with the powder. The volume-filling rate of thepowder was about 25%. In this connection, respective steps of weighing,mixing, and molding of the powders were all conducted in a globe boxcapable of maintaining a nitrogen atmosphere having a moisture contentof 1 ppm or less and an oxygen content of 1 ppm or less.

The mixed powder was placed in a crucible made of boron nitride and setin a graphite resistive heating-type electric furnace. The bakingoperations were conducted as follows: the baking atmosphere was firstvacuumed by a diffusion pump, heated from room temperature to 800° C. ata rate of 500° C. per hour, and pressurized to 1 MPa by introducingnitrogen having a purity of 99.999% by volume at 800° C., and thetemperature was elevated to 1800° C. at a rate of 500° C. per hour andheld at 1800° C. for 2 hours.

After baking, the resulting baked product was roughly pulverized andthen was pulverized by hand using a crucible and mortar made of siliconnitride sintered compact, followed by filtering through a sieve having amesh of 30 μm. When the particle distribution was measured, the averageparticle size was found to be 15 μm.

The constitutive crystal phase of the resulting synthetic powder wasidentified according to the following procedure. First, in order toobtain pure CaAlSiN₃ containing no M Element as a standard substance,the silicon nitride powder, the aluminum nitride powder, and the calciumnitride powder were weighed so as to be 34.088% by weight, 29.883% byweight, and 36.029% by weight, respectively, followed by 30 minutes ofmixing by means of an agate mortar and pestle in a globe box. Then, themixture was placed in a crucible made of boron nitride and set in agraphite resistive heating-type electric furnace. The baking operationswere conducted as follows: the baking atmosphere was first vacuumed by adiffusion pump, heated from warm room to 800° C. at a rate of 500° C.per hour, and pressurized to 1 MPa by introducing nitrogen having apurity of 99.999% by volume at 800° C., and the temperature was elevatedto 1800° C. at a rate of 500° C. per hour and held at 1800° C. for 2hours. The synthesized sample was pulverized by means of an agate mortarand then measurement of powder X-ray diffraction was conducted using Kαline of Cu. As a result, the resulting chart shows a pattern illustratedin FIG. 1-1 and the compound was judged to be a CaAlSiN₃ crystal phasebased on indexing shown in Table 4. The crystal phase is an orthorhombicsystem, which has lattice constants of a=9.8007 (4) Å, b=5.6497 (2) Å,and c=5. 0627 (2) Å. A space group determined by convergent beamelectron diffraction using TEM is Cmc2₁ (36th space group ofInternational Tables for Crystallography). Furthermore, the atomiccoordinate position of each element determined by the Rietveld analysisusing the space group is as shown in Table 5. The measured intensity ofX-ray diffraction and the calculated intensity computed by the Rietveldmethod from the atomic coordinates show a good coincidence as shown inTable 4.

Next, the synthesized compound represented by the composition formula:Eu_(0.008)Ca_(0.992)AlSiN₃ was pulverized by means of an agate mortarand then measurement of powder X-ray diffraction was conducted using Kαline of Cu. As a result, the resulting chart is shown in FIG. 1-2 andthe compound was judged to be a CaAlSiN₃ family crystal phase based onindexing shown in Table 4.

The composition analysis of the powder was conducted by the followingmethod. First, 50 mg of the sample was placed in a platinum crucible and0.5 g of sodium carbonate and 0.2 g of boric acid were added thereto,followed by heating and melting the whole. Thereafter, the melt wasdissolved in 2 ml of hydrochloric acid to be a constant volume of 100ml, whereby a solution for measurement was prepared. By subjecting theliquid sample to ICP emission spectrometry, the amounts of Si, Al, Eu,and Ca in the powder sample were quantitatively determined. Moreover, 20mg of the sample was charged into a Tin capsule, which was then placedin a nickel basket. Then, using TC-436 Model oxygen and nitrogenanalyzer manufactured by LECO, oxygen and nitrogen in the powder samplewere quantitatively determined. The results of the measurement were asfollows: Eu: 0.86±0.01% by weight, Ca: 28.9±0.1% by weight, Si:20.4±0.1-% by weight, Al: 19.6±0.1% by weight, N: 28.3±0.2% by weight,O: 2.0±0.1% by weight. In comparison with the indicated % by weight inthe designed composition shown in Table 2, an oxygen content isespecially high. The reason therefor is attributed to impurity oxygencontained in silicon nitride, aluminum nitride, and calcium nitride,which were employed as raw materials. In this composition, the ratio ofnumber of atoms of N and O, N/(O+N) corresponds to 0.942. Thecomposition of the synthesized inorganic compound calculated from theanalytical results of all the elements isEu_(0.0078)Ca_(0.9922)Si_(0.9997)Al_(0.9996)N_(2.782)O_(0.172). In theinvention, one wherein part of N is replaced with O is also included inthe scope of the invention and, even in that case, a high-luminance redphosphor is obtained.

As a result of irradiation of the powder with a lamp emitting a lighthaving a wavelength of 365 nm, emission of a red light was confirmed. Asa result of measurement of emission spectrum (FIG. 4) and excitationspectrum (FIG. 5) of the powder using a fluorescence spectrophotometer,with regard to the peak wavelengths of the excitation and emissionspectra (Table 6), it was found that the peak of the excitation spectrumwas present at 449 nm and it was a phosphor having a peak at a red lightof 653 nm in the emission spectrum with excitation at 449 nm. Theemission intensity of the peak was 10655 counts. In this connection,since the count value varies depending on the measuring apparatus andconditions, the unit is an arbitrary unit. Moreover, the CIEchromaticity determined from the emission spectrum with excitation at449 nm was red color of x=0.6699 and y=0.3263.

TABLE 1 Parameters for designed composition M Element A Element DElement E Element X Element Eu Mg Ca Sr Ba Si Al N Example a Value bValue c Value d Value e Value 1 0.008 0 0.992 0 0 1 1 3 2 0.008 0 0 00.992 1 1 3 3 0.008 0 0.1984 0 0.7936 1 1 3 4 0.008 0 0.3968 0 0.5952 11 3 5 0.008 0 0.5952 0 0.3968 1 1 3 6 0.008 0 0.7936 0 0.1984 1 1 3 70.008 0 0.8928 0 0.0992 1 1 3 8 0.008 0 0.8928 0.0992 0 1 1 3 9 0.008 00.7936 0.1984 0 1 1 3 10 0.008 0 0.6944 0.2976 0 1 1 3 11 0.008 0 0.59520.3968 0 1 1 3 12 0.008 0 0.496 0.496 0 1 1 3 13 0.008 0 0.3968 0.5952 01 1 3 14 0.008 0 0.1984 0.7936 0 1 1 3 15 0.008 0 0 0.992 0 1 1 3 160.008 0.0992 0.8928 0 0 1 1 3 17 0.008 0.1984 0.7936 0 0 1 1 3 18 0.0080.2976 0.6944 0 0 1 1 3 19 0.008 0.3968 0.5952 0 0 1 1 3 20 0.008 0.4960.496 0 0 1 1 3 21 0.008 0.5952 0.3968 0 0 1 1 3 22 0.008 0.6944 0.29760 0 1 1 3 23 0.008 0.7936 0.1984 0 0 1 1 3 24 0.008 0.8928 0.0992 0 0 11 3 25 0.008 0.992 0 0 0 1 1 3

TABLE 2 Designed composition (% by weight) Example Eu Mg Ca Sr Ba Si AlN 1 0.88056 0 28.799 0 0 20.3393 19.544 30.4372 2 0.51833 0 0 0 58.088711.9724 11.5042 17.9163 3 0.56479 0 3.69436 0 50.6371 13.0457 12.535619.5225 4 0.62041 0 8.11634 0 41.7178 14.3304 13.77 21.4451 5 0.68818 013.5044 0 30.8499 15.8958 15.2742 23.7876 6 0.77257 0 20.2139 0 17.316517.8451 17.1473 26.7047 7 0.82304 0 24.2261 0 9.2238 19.0107 18.267328.449 8 0.85147 0 25.063 6.08788 0 19.6674 18.8984 29.4318 9 0.82425 021.5659 11.7864 0 19.0386 18.2941 28.4907 10 0.79871 0 18.2855 17.1319 018.4487 17.7273 27.608 11 0.7747 0 15.2022 22.156 0 17.8943 17.194526.7783 12 0.7521 0 12.2989 26.887 0 17.3722 16.6929 25.997 13 0.73078 09.56019 31.3497 0 16.8797 16.2196 25.26 14 0.69157 0 4.52361 39.5568 015.974 15.3494 23.9047 15 0.65635 0 0 46.928 0 15.1605 14.5677 22.687416 0.89065 1.76643 26.2163 0 0 20.5725 19.768 30.7862 17 0.90098 3.5738323.5736 0 0 20.8111 19.9973 31.1432 18 0.91155 5.42365 20.869 0 021.0553 20.2319 31.5086 19 0.92238 7.3174 18.1001 0 0 21.3052 20.472231.8828 20 0.93346 9.25666 15.2646 0 0 21.5612 20.7181 32.2659 210.94481 11.2431 12.3602 0 0 21.8235 20.9701 32.6583 22 0.95645 13.27849.3843 0 0 22.0922 21.2283 33.0604 23 0.96837 15.3645 6.33418 0 022.3676 21.4929 33.4725 24 0.98059 17.5033 3.20707 0 0 22.6499 21.764233.895 25 0.99313 19.6967 0 0 0 22.9394 22.0425 34.3283

TABLE 3 Mixing composition (% by weight) Example EuN Mg3N2 Ca3N2 Sr3N2Ba3N2 Si3N4 AlN 1 0.96147 0 35.4993 0 0 33.8578 29.6814 2 0.56601 0 0 062.0287 19.932 17.4733 3 0.61675 0 4.55431 0 54.0709 21.7185 19.0395 40.67747 0 10.0054 0 44.546 23.8569 20.9142 5 0.75146 0 16.6472 0 32.940626.4624 23.1982 6 0.84359 0 24.9176 0 18.4896 29.7068 26.0424 7 0.898680 29.863 0 9.84853 31.6467 27.7431 8 0.92972 0 30.8943 6.73497 0 32.739728.7012 9 0.9 0 26.5838 13.0394 0 31.6931 27.7837 10 0.87212 0 22.540318.9531 0 30.7114 26.9231 11 0.84592 0 18.7397 24.5116 0 29.7886 26.114212 0.82124 0 15.1609 29.7457 0 28.9197 25.3524 13 0.79797 0 11.78534.6832 0 28.1 24.6339 14 0.75516 0 5.57638 43.7635 0 26.5926 23.3124 150.71671 0 0 51.9191 0 25.2387 22.1255 16 0.97249 2.44443 32.3156 0 034.2459 30.0216 17 0.98377 4.94555 29.058 0 0 34.6429 30.3697 18 0.995317.50535 25.724 0 0 35.0493 30.726 19 1.00712 10.1259 22.3109 0 0 35.465431.0907 20 1.01922 12.8095 18.8158 0 0 35.8914 31.4642 21 1.0316115.5582 15.2356 0 0 36.3278 31.8467 22 1.04431 18.3747 11.5674 0 036.7749 32.2387 23 1.05732 21.2613 7.80768 0 0 37.2332 32.6404 241.07067 24.2208 3.9531 0 0 37.7031 33.0523 25 1.08435 27.256 0 0 038.1849 33.4748

TABLE 4-1 Results of X-ray diffraction (No. 1) Observed Calculatedintensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h kl degree Å unit unit 1 2 0 0 18.088 4.90033 1129 360 2 1 1 0 18.1094.89464 3960 1242 3 2 0 0 18.133 4.90033 569 178 4 1 1 0 18.154 4.894641993 614 5 1 1 1 25.288 3.51896 3917 5137 6 1 1 1 25.352 3.51896 19622539 7 3 1 0 31.61 2.82811 72213 68028 8 0 2 0 31.648 2.82483 3870036445 9 3 1 0 31.691 2.82811 35723 33624 10 0 2 0 31.729 2.82483 1915818014 11 0 0 2 35.431 2.53137 75596 78817 12 0 0 2 35.522 2.53137 3757939097 13 3 1 1 36.357 2.469 100000 101156 14 0 2 1 36.391 2.4668 5628356923 15 3 1 1 36.451 2.469 49334 49816 16 0 2 1 36.484 2.4668 2787328187 17 4 0 0 36.647 2.45017 15089 15187 18 2 2 0 36.691 2.44732 1143011483 19 4 0 0 36.741 2.45017 7481 7507 20 2 2 0 36.785 2.44732 56615676 21 2 0 2 40.058 2.24902 5403 5599 22 1 1 2 40.068 2.24847 76 79 232 0 2 40.162 2.24902 2678 2767 24 1 1 2 40.172 2.24847 38 39 25 2 2 140.924 2.20339 14316 13616 26 2 2 1 41.031 2.20339 7123 6730 27 3 1 248.207 1.88616 21363 21434 28 0 2 2 48.233 1.88519 19002 19072 29 3 1 248.334 1.88616 10584 10591 30 0 2 2 48.361 1.88519 9407 9424 31 5 1 049.159 1.85184 2572 2513 32 4 2 0 49.185 1.85092 4906 4795 33 1 3 049.228 1.84939 253 239 34 5 1 0 49.289 1.85184 1346 1242 35 4 2 0 49.3151.85092 2565 2369 36 1 3 0 49.359 1.84939 130 118 37 4 0 2 51.8921.76054 6201 6580 38 2 2 2 51.926 1.75948 6187 6564 39 4 0 2 52.0311.76054 3075 3251 40 2 2 2 52.064 1.75948 3078 3243 41 5 1 1 52.5791.73915 2042 2153 42 4 2 1 52.604 1.73839 188 199 43 1 3 1 52.6451.73712 282 298 44 5 1 1 52.72 1.73915 1002 1064 45 4 2 1 52.745 1.7383992 98 46 1 3 1 52.786 1.73712 139 147 47 6 0 0 56.272 1.63344 1772117283 48 3 3 0 56.344 1.63155 33576 32772 49 6 0 0 56.425 1.63344 87578541 50 3 3 0 56.496 1.63155 16569 16195

TABLE 4-2 Results of X-ray diffraction (No. 2) Observed Calculatedintensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h kl degree Å unit unit 51 1 1 3 57.738 1.59541 771 461 52 1 1 3 57.8951.59541 447 228 53 3 3 1 59.475 1.5529 987 445 54 3 3 1 59.638 1.5529504 220 55 5 1 2 62.045 1.4946 421 460 56 4 2 2 62.068 1.49412 3824 417457 1 3 2 62.105 1.49331 518 571 58 5 1 2 62.217 1.4946 209 227 59 4 2 262.239 1.49412 1886 2063 60 1 3 2 62.276 1.49331 257 282 61 3 1 3 64.2181.44918 25890 27958 62 0 2 3 64.239 1.44874 19133 20597 63 3 1 3 64.3961.44918 12851 13816 64 0 2 3 64.418 1.44874 9441 10178 65 6 2 0 66.0131.41406 6643 6534 66 0 4 0 66.099 1.41242 2793 2737 67 6 2 0 66.1981.41406 3327 3229 68 0 4 0 66.284 1.41242 1385 1353 69 2 2 3 67.3441.3893 3814 3509 70 2 2 3 67.534 1.3893 1869 1735 71 6 0 2 68.281 1.372518466 17968 72 3 3 2 68.345 1.37138 27397 26670 73 6 0 2 68.474 1.37259086 8881 74 3 3 2 68.538 1.37138 13419 13182 75 6 2 1 68.885 1.3619322014 21698 76 0 4 1 68.97 1.36046 11088 10930 77 7 1 0 69.056 1.35899827 815 78 6 2 1 69.081 1.36193 10883 10725 79 5 3 0 69.112 1.35802 573564 80 2 4 0 69.161 1.35717 4360 4307 81 0 4 1 69.166 1.36046 5470 540382 7 1 0 69.252 1.35899 409 403 83 5 3 0 69.308 1.35802 283 279 84 2 4 069.358 1.35717 2165 2129 85 7 1 1 71.871 1.31252 263 170 86 5 3 1 71.9261.31165 684 445 87 2 4 1 71.974 1.31088 810 520 88 7 1 1 72.077 1.31252132 84 89 5 3 1 72.133 1.31165 345 220 90 2 4 1 72.181 1.31088 399 25791 0 0 4 74.975 1.26568 3881 3841 92 0 0 4 75.194 1.26568 1960 1899 93 51 3 76.274 1.24734 1812 1659 94 4 2 3 76.294 1.24705 865 798 95 1 3 376.328 1.24659 516 478 96 5 1 3 76.497 1.24734 826 820 97 4 2 3 76.5181.24705 403 395 98 1 3 3 76.552 1.24659 241 237 99 6 2 2 77.212 1.23456989 7316 100 0 4 2 77.293 1.23341 1114 1179

TABLE 4-3 Results of X-ray diffraction (No. 3) Observed Calculatedintensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h kl degree Å unit unit 101 6 2 2 77.439 1.2345 3384 3619 102 0 4 2 77.5211.23341 542 583 103 2 0 4 77.888 1.22547 2080 2260 104 1 1 4 77.8951.22538 237 253 105 8 0 0 77.917 1.22508 32 35 106 4 4 0 78.025 1.22366144 155 107 2 0 4 78.118 1.22547 1016 1118 108 1 1 4 78.125 1.22538 113125 109 8 0 0 78.148 1.22508 16 17 110 4 4 0 78.256 1.22366 69 77 111 71 2 80.08 1.19735 671 762 112 5 3 2 80.134 1.19668 45 51 113 2 4 2 80.181.1961 2092 2383 114 7 1 2 80.32 1.19735 332 377 115 5 3 2 80.3731.19668 22 25 116 2 4 2 80.42 1.1961 1032 1179 117 4 4 1 80.724 1.189411023 1169 118 4 4 1 80.966 1.18941 504 579 119 3 3 3 82.095 1.17299 566560 120 3 3 3 82.343 1.17299 249 277 121 3 1 4 83.634 1.15527 2395 2418122 0 2 4 83.654 1.15504 2611 2637 123 3 1 4 83.889 1.15527 1191 1197124 0 2 4 83.909 1.15504 1309 1306 125 4 0 4 86.47 1.12451 531 492 126 22 4 86.496 1.12423 1172 1090 127 8 2 0 86.525 1.12394 278 258 128 7 3 086.558 1.12359 934 864 129 1 5 0 86.663 1.1225 737 688 130 4 0 4 86.7381.12451 262 244 131 2 2 4 86.765 1.12423 585 540 132 8 2 0 86.7931.12394 139 128 133 7 3 0 86.826 1.12359 467 428 134 1 5 0 86.932 1.1225367 341 135 8 0 2 88.617 1.10273 102 99 136 4 4 2 88.722 1.10169 10941054 137 8 0 2 88.895 1.10273 50 49 138 4 4 2 89.001 1.10169 525 523 1398 2 1 89.18 1.09723 495 480 140 7 3 1 89.213 1.09691 551 552 141 1 5 189.318 1.09588 123 123 142 8 2 1 89.461 1.09723 239 238 143 7 3 1 89.4941.09691 271 274 144 1 5 1 89.6 1.09588 60 61 145 6 2 3 90.581 1.083868698 8736 146 0 4 3 90.66 1.08312 4187 4201 147 6 2 3 90.869 1.083864305 4332 148 0 4 3 90.949 1.08312 2067 2083 149 9 1 0 92.171 1.06928921 787 150 6 4 0 92.269 1.06839 820 696

TABLE 4-4 Results of X-ray diffraction (No. 4) Observed Calculatedintensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h kl degree Å unit unit 151 3 5 0 92.329 1.06786 846 709 152 9 1 0 92.4671.06928 466 390 153 6 4 0 92.566 1.06839 403 346 154 3 5 0 92.6261.06786 407 352 155 7 1 3 93.395 1.05845 882 812 156 5 3 3 93.448 1.0581111 1042 157 2 4 3 93.494 1.05759 575 533 158 7 1 3 93.697 1.05845 439403 159 5 3 3 93.75 1.058 557 517 160 2 4 3 93.797 1.05759 286 264 161 91 1 94.828 1.0462 8091 7983 162 6 4 1 94.928 1.04537 8273 8175 163 5 1 494.979 1.04494 392 387 164 3 5 1 94.987 1.04487 8587 8469 165 4 2 494.999 1.04477 1156 1143 166 1 3 4 95.032 1.0445 609 602 167 9 1 195.139 1.0462 4016 3962 168 6 4 1 92.238 1.04537 4108 4058 169 5 1 495.29 1.04494 195 192 170 3 5 1 95.298 1.04487 4269 4204 171 4 2 4 95.311.04477 575 567 172 1 3 4 95.344 1.0445 304 299 173 8 2 2 97.156 1.02724533 515 174 7 3 2 97.189 1.02697 983 946 175 1 5 2 97.296 1.02613 878840 176 8 2 2 97.479 1.02724 264 256 177 7 3 2 97.513 1.02697 482 470178 1 5 2 97.62 1.02613 426 417 179 6 0 4 100.691 1.00049 5749 5826 1803 3 4 100.751 1.00005 7565 7696 181 6 0 4 101.035 1.00049 2904 2897 1823 3 4 101.096 1.00005 3864 3826 183 1 1 5 101.945 0.99155 99 95 184 4 43 102.075 0.99064 700 665 185 1 1 5 102.297 0.99155 50 47 186 4 4 3102.428 0.99064 353 331 187 9 1 2 102.889 0.98501 2904 2773 188 6 4 2102.99 0.98431 1613 1539 189 3 5 2 103.051 0.9839 2352 2255 190 9 1 2103.247 0.98501 1414 1379 191 6 4 2 103.349 0.98431 774 766 192 3 5 2103.41 0.9839 1122 1122 193 10 0 0 103.617 0.98007 899 903 194 5 5 0103.786 0.97893 803 806 195 10 0 0 103.979 0.98007 451 449 196 5 5 0104.15 0.97893 411 401 197 5 5 1 106.535 0.96113 323 378 198 5 5 1106.917 0.96113 183 188 199 3 1 5 107.807 0.95329 6210 6468 200 0 2 5107.827 0.95316 3757 3932

TABLE 4-5 Results of X-ray diffraction (No. 5) Observed Calculatedintensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h kl degree Å unit unit 201 3 1 5 108.198 0.95329 3120 3223 202 0 2 5108.219 0.95316 1888 1959 203 6 2 4 109.525 0.94308 3209 2974 204 9 3 0109.591 0.9427 3570 3280 205 0 4 4 109.609 0.9426 656 602 206 0 6 0109.779 0.94161 1454 1338 207 6 2 4 109.93 0.94308 1622 1483 208 9 3 0109.995 0.9427 1792 1636 209 0 4 4 110.014 0.9426 329 300 210 0 6 0110.185 0.94161 731 667 211 2 2 5 110.828 0.93563 247 223 212 8 2 3110.859 0.93546 1336 1210 213 7 3 3 110.894 0.93526 103 93 214 1 5 3111.007 0.93463 519 457 215 2 2 5 111.242 0.93563 119 111 216 8 2 3111.273 0.93546 647 604 217 7 3 3 111.308 0.93526 49 46 218 1 5 3111.422 0.93463 246 228 219 9 3 1 112.432 0.92677 457 453 220 7 1 4112.538 0.9262 96 97 221 10 2 0 112.59 0.92592 528 532 222 5 3 4 112.5950.9259 832 826 223 0 6 1 112.625 0.92574 381 385 224 2 4 4 112.6450.92563 174 173 225 8 4 0 112.676 0.92546 1400 1394 226 2 6 0 112.8190.92469 115 117 227 9 3 1 112.859 0.92677 222 226 228 7 1 4 112.9660.9262 47 48 229 10 2 0 113.018 0.92592 261 265 230 5 3 4 113.023 0.9259405 412 231 0 6 1 113.053 0.92574 188 192 232 2 4 4 113.074 0.92563 8687 233 8 4 0 113.105 0.92546 688 696 234 2 6 0 113.249 0.92469 56 59 23510 0 2 114.874 0.91396 1273 1144 236 5 5 2 115.055 0.91303 1086 961 23710 0 2 115.321 0.91396 627 571 238 10 2 1 115.495 0.91081 149 143 239 55 2 115.504 0.91303 501 480 240 8 4 1 115.583 0.91038 71 69 241 2 6 1115.729 0.90965 825 800 242 10 2 1 115.948 0.91081 76 71 243 8 4 1116.036 0.91038 36 34 244 2 6 1 116.184 0.90965 418 400 245 9 1 3117.036 0.90323 3785 3707 246 6 4 3 117.147 0.9027 6351 6249 247 3 5 3117.214 0.90238 8809 8688 248 9 1 3 117.503 0.90323 1876 1854 249 6 4 3117.615 0.9027 3153 3125 250 3 5 3 117.682 0.90238 4393 4345

TABLE 4-6 Results of X-ray diffraction (No. 6) Observed Calculatedintensity intensity Peak Indices 2θ Spacing arbitrary arbitrary No. h kl degree Å unit unit 251 5 1 5 120.23 0.88842 190 173 252 4 2 5 120.2530.88831 1117 1030 253 1 3 5 120.291 0.88814 215 197 254 5 1 5 120.7270.88842 92 87 255 4 2 5 120.751 0.88831 556 516 256 1 3 5 120.7890.88814 107 99 257 9 3 2 121.365 0.88343 9276 8712 258 0 6 2 121.5730.88253 3149 2999 259 9 3 2 121.874 0.88343 4581 4365 260 0 6 2 122.0850.88253 1548 1503 261 8 0 4 122.102 0.88027 825 792 262 11 1 0 122.1440.88009 48 46 263 4 4 4 122.227 0.87974 1161 1113 264 7 5 0 122.3310.8793 55 53 265 4 6 0 122.416 0.87894 35 34 266 8 0 4 122.619 0.88027411 397 267 11 1 0 122.661 0.88009 23 23 268 4 4 4 122.745 0.87974 570558 269 7 5 0 122.85 0.8793 27 26 270 4 6 0 122.937 0.87894 17 17 271 102 2 124.703 0.86958 1189 1160 272 8 4 2 124.8 0.86919 1867 1838 273 2 62 124.96 0.86856 465 456 274 10 2 2 125.249 0.86958 604 582 275 11 1 1125.334 0.86709 855 833 276 8 4 2 125.347 0.86919 947 923 277 2 6 2125.509 0.86856 234 229 278 7 5 1 125.528 0.86633 30 29 279 4 6 1125.617 0.86599 2025 1984 280 11 1 1 125.888 0.86709 430 418 281 7 5 1126.084 0.86633 15 15 282 4 6 1 126.174 0.86599 1035 996 283 3 3 5127.101 0.86033 236 232 284 3 3 5 127.677 0.86033 128 117

TABLE 5 Data of crystal structure of CaAlSiN3 CaAlSiN3 Space Group (#36)Cmc2₁ Lattice constants (Å) a b c 9.8007(4) 5.6497(2) 5.0627(2) Site x yz Si/Al 8(b) 0.1734(2) 0.1565(3) 0.0504(4) N1 8(b) 0.2108(4) 0.1205(8)0.3975(2) N2 4(a) 0 0.2453(7) 0.0000(10) Ca 4(a) 0 0.3144(3) 0.5283SiN2O Space Group (#36) Cmc2₁ Lattice constants (Å) a b c 8.8717 5.49094.8504 Site x y z Si 8(b) 0.1767 0.1511 0.0515 N 8(b) 0.2191 0.12280.3967 O 4(a) 0 0.2127 0

TABLE 6 Peak wavelength and intensity of excitation · emission spectraEmission Emission Excitation Excitation intensity wavelength intensitywavelength Example arbitrary unit nm arbitrary unit nm 1 10655 653 10595449 2 622 600 617 426 3 2358 655 2336 449 4 4492 655 4471 449 5 5985 6555975 449 6 6525 654 6464 449 7 6796 654 6748 449 8 8457 654 8347 449 98384 650 8278 449 10 7591 650 7486 449 11 7368 645 7264 449 12 7924 6417834 449 13 8019 637 7920 449 14 8174 629 8023 449 15 1554 679 1527 40116 8843 657 8779 449 17 5644 658 5592 449 18 6189 658 6199 449 19 5332657 5261 449 20 5152 661 5114 449 21 4204 663 4177 449 22 3719 667 3710449 23 3800 664 3833 449 24 2090 679 2097 449 25 322 679 326 453

Comparative Example 1

Using the raw powders described in Example 1, in order to obtain pureCaAlSiN₃ containing no M Element, the silicon nitride powder, thealuminum nitride powder, and the calcium nitride powder were weighed soas to be 34.088% by weight, 29.883% by weight, and 36.029% by weight,respectively, and a powder was prepared in the same manner as inExample 1. According to the measurement of X-ray diffraction, it wasconfirmed that the synthesized powder was CaAlSiN₃. When excitation andemission spectra of the synthesized inorganic compound were measured,any remarkable emission peak was not observed in the range of 570 nm to700 nm.

Examples 2 to 7

As Examples 2 to 7 were prepared inorganic compounds having acomposition in which part or all of Ca was replaced with Ba.

The inorganic compounds were prepared in the same manner as in Example 1with the exception of the compositions shown in Tables 1, 2, and 3.According to the measurement of X-ray diffraction, it was confirmed thatthe synthesized powders were inorganic compounds having the same crystalstructure as that of CaAlSiN₃. When excitation and emission spectra ofthe synthesized inorganic compound were measured, as shown in FIGS. 4and 5, and Table 6, it was confirmed that they were red phosphors havingan emission peak in the range of 570 nm to 700 nm, which were excitedwith an ultraviolet ray or a visible light of 350 nm to 600 nm.Incidentally, since emission luminance decreases as an added amount ofBa increases, a composition in the region where the added amount of Bais small is preferred.

Examples 8 to 15

As Examples 8 to 15 were prepared inorganic compounds having acomposition in which part or all of Ca was replaced with Sr.

Phosphors were prepared in the same manner as in Example 1 with theexception of the compositions shown in Tables 1, 2, and 3. According tothe measurement of X-ray diffraction, it was confirmed that thesynthesized powders were inorganic compounds having the same crystalstructure as that of CaAlSiN₃. When excitation and emission spectra ofthe synthesized inorganic compound were measured, as shown in FIGS. 6and 7 (Examples 8 to 11), FIGS. 8 and 9 (Examples 12 to 15), and Table6, it was confirmed that they were red phosphors having an emission peakin the range of 570 nm to 700 nm, which were excited with an ultravioletray or a visible light of 350 nm to 600 nm. Incidentally, emissionluminance decreases as an added amount of Sr increases, but thewavelength of the emission peak shifts to a shorter wavelength side ascompared with the addition of Ca alone. Therefore, in the case that itis desired to obtain a phosphor having a peak wavelength in the range of600 nm to 650 nm, it is effective to replace part of Ca with Sr.

Examples 16 to 25

As Examples 16 to 25 were prepared inorganic compounds having acomposition in which part or all of Ca was replaced with Mg.

Phosphors were prepared in the same manner as in Example 1 with theexception of the compositions shown in Tables 1, 2, and 3. According tothe measurement of X-ray diffraction, it was confirmed that thesynthesized powders were inorganic compounds having the same crystalstructure as that of CaAlSiN₃. When excitation and emission spectra ofthe synthesized inorganic compound were measured, as shown in FIGS. 10and 11, and Table 6, it was confirmed that they were red phosphorshaving an emission peak in the range of 570 nm to 700 nm, which wereexcited with an ultraviolet ray or a visible light of 350 nm to 600 nm.Incidentally, since emission luminance decreases as an added amount ofMg increases, a composition in the region where the added amount of Mgis small is preferred.

Examples 26 to 30

As Examples 26 to 30 were prepared inorganic compounds having acomposition in which part of N was replaced with O. In this case, sincevalence number is different between N and O, simple replacement does notresult in neutrality of the total charge. Thus, the composition:Ca ₆ Si _(6−x) Al _(6+x) O _(x) N _(18−x) (0<x≤3)was investigated, which is a composition in which Si—N is replaced withAl—O.

Phosphors were prepared in the same manner as in Example 1 with theexception of the compositions shown in Tables 7 and 8. According to themeasurement of X-ray diffraction, it was confirmed that the synthesizedpowders were inorganic compounds having the same crystal structure asthat of CaAlSiN₃. When excitation and emission spectra of thesynthesized inorganic compound were measured, as shown in FIGS. 12 and13, it was confirmed that they were red phosphors having an emissionpeak in the range of 570 nm to 700 nm, which were excited with anultraviolet ray or a visible light of 350 nm to 600 nm. Incidentally,since emission luminance decreases as an added amount of oxygenincreases, a composition in the region where the added amount of oxygenis small is preferred.

TABLE 7 Parameters for designed composition M Element A Element DElement E Element X Element Eu Ca Si Al O N Example a Value b Value cValue d Value e Value 26 0.008 0.992 0.916667 1.083333 0.083333 2.91933327 0.008 0.992 0.833333 1.166667 0.166667 2.836 28 0.008 0.992 0.75 1.250.25 2.752667 29 0.008 0.992 0.666667 1.333333 0.333333 2.669333 300.008 0.992 0.5 1.5 0.5 2.502667

TABLE 8 Mixing composition (% by weight) Example Si3N4 AlN Al203 Ca3N2EuN 26 31.02 30.489 2.05 35.48 0.961 27 28.184 31.297 4.097 35.461 0.9628 25.352 32.103 6.143 35.442 0.96 29 22.523 32.908 8.186 35.423 0.95930 16.874 34.517 12.266 35.385 0.958

Examples 31 to 37

Using the same raw powders as in Example 1, in order to obtain inorganiccompounds (showing mixing compositions of the raw powders in Table 9 andcomposition parameters in Table 10), the silicon nitride powder, thealuminum nitride powder, the calcium nitride powder, and the europiumnitride powder were weighed, followed by 30 minutes of mixing by meansof an agate mortar and pestle. Thereafter, the resulting mixture wasmolded using a mold by applying a pressure of 20 MPa to form a moldedarticle having a diameter of 12 mm and a thickness of 5 mm. In thisconnection, respective steps of weighing, mixing, and molding of thepowders were all conducted in a globe box capable of maintaining anitrogen atmosphere having a moisture content of 1 ppm or less and anoxygen content of 1 ppm or less.

The molded article was placed in a crucible made of boron nitride andset in a graphite resistive heating-type electric furnace. The bakingoperations were conducted as follows: the baking atmosphere was firstvacuumed by a diffusion pump, heated from warm room to 800° C. at a rateof 500° C. per hour, and pressurized to 1 MPa by introducing nitrogenhaving a purity of 99.9991; by volume at 800° C., and the temperaturewas elevated to 1800° C. at a rate of 500° C. per hour and held at 1800°C. for 2 hours.

After baking, as a result of identification of constitutive crystalphase of the resulting sintered compact, it was judged to be a CaAlSiN₃family crystal phase. As a result of irradiation of the powder with alamp emitting a light having a wavelength of 365 nm, it was confirmedthat it emits a red light. When excitation spectrum and emissionspectrum of the powder were measured using a fluorescencespectrophotometer, as shown in Table 11, it was confirmed that it was ared phosphor having an emission peak in the range of 570 nm to 700 nm,which was excited with an ultraviolet ray or a visible light of 350 nmto 600 nm. Incidentally, since the measurement in these Examples wasconducted using an apparatus different from that used in other Examples,the count values can be compared only within the range of Examples 31 to37.

TABLE 9 Mixing composition of raw powder (unit: % by weight) Si3N4 AlNCa3N2 EuN Example 31 34.07348 29.870475 35.995571 0.060475 Example 3234.059016 29.857795 35.962291 0.120898 Example 33 34.030124 29.83246735.895818 0.241591 Example 34 33.518333 29.383806 34.718285 2.379577Example 35 33.185606 29.092121 33.952744 3.769529 Example 36 32.43435128.433534 32.224251 6.907864 Example 37 31.418284 27.542801 29.88647811.152437

TABLE 10 Parameters for designed composition a(Eu) b(Ca) c(Si) d(Al)e(N) Example 31 0.0005 0.9995 1 1 3 Example 32 0.001 0.999 1 1 3 Example33 0.002 0.998 1 1 3 Example 34 0.02 0.98 1 1 3 Example 35 0.032 0.968 11 3 Example 36 0.06 0.94 1 1 3 Example 37 0.1 0.9 1 1 3

TABLE 11 Peak wavelength and intensity of excitation and emissionspectra on fluorescence measurement Excitation spectrum Emissionspectrum Peak Intensity Peak Intensity wavelength arbitrary wavelengtharbitrary nm unit nm unit Example 31 479.6 387.322 609.2 391.066 Example32 472.8 374.967 609.4 375.33 Example 33 480 427.41 612.6 428.854Example 34 538 412.605 626.8 411.394 Example 35 546.4 414.434 629.2413.009 Example 36 549.8 181.127 638.8 180.981 Example 37 549.4 89.023644.4 92.763

Examples 38 to 56 and 60 to 76

As Examples 38 to 56 and 60 to 76 were prepared inorganic compoundshaving compositions in which c, d, and e parameters in theEu_(a)Ca_(b)Si_(c)Al_(d)N_(e) composition were changed.

Phosphors were prepared in the same manner as in Example 1 with theexception of the compositions shown in Tables 12 and 13. According tothe measurement of X-ray diffraction, it was confirmed that thesynthesized powders were powders containing inorganic compounds havingthe same crystal structure as that of CaAlSiN₃. When excitation andemission spectra of the synthesized inorganic compound were measured, asshown in Table 14, it was confirmed that they were red phosphors havingan emission peak in the range of 570 nm to 700 nm, which were excitedwith an ultraviolet ray or a visible light of 350 nm to 600 nm.

TABLE 12 Parameters for designed composition a Value b Value c Value dValue e Value Example (Eu) (Ca) (Si) (Al) (N) 38 0.002 0.998 1 1 3 390.004 0.996 1 1 3 40 0.008 0.992 1 1 3 41 0.01 0.99 1 1 3 42 0.06 0.94 11 3 43 0.2 0.8 1 1 3 44 0.0107 0.9893 1 2 3 45 0.0133 0.9867 1 3 3 460.016 0.984 1 4 3 47 0.0187 0.9813 1 5 3 48 0.0213 0.9787 1 6 3 490.0107 0.9893 2 1 3 50 0.0133 0.9867 2 2 3 51 0.016 0.984 2 3 3 520.0187 0.9813 2 4 3 53 0.0213 0.9787 2 5 3 54 0.024 0.976 2 6 3 550.0133 0.9867 3 1 3 56 0.016 0.984 4 1 3 60 0.016 0.984 3 2 3 61 0.0190.981 3 3 3 62 0.013 2.987 1 1 3 63 0.013 1.987 2 1 3 64 0.016 2.984 2 13 65 0.016 1.984 3 1 3 66 0.019 2.981 3 1 3 67 0.013 1.987 1 2 3 680.016 2.984 1 2 3 69 0.019 2.981 2 2 3 70 0.019 1.981 3 2 3 71 0.0212.979 3 2 3 72 0.016 1.984 1 3 3 73 0.019 2.981 1 3 3 74 0.019 1.981 2 33 75 0.021 2.979 2 3 3 76 0.021 1.979 3 3 3

TABLE 13 Mixing composition of raw powder (unit: % by weight) ExampleSi3N4 AlN Ca3N2 EuN 38 34.01 29.81 35.94 0.24 39 33.925 29.74 35.8550.48 40 33.765 29.595 35.68 0.96 41 33.685 29.525 35.595 1.195 42 31.78527.86 33.59 6.77 43 27.45 24.06 29.01 19.485 44 25.99 45.56 27.465 0.98545 21.125 55.55 22.325 1 46 17.795 62.39 18.805 1.01 47 15.37 67.36516.245 1.02 48 13.53 71.15 14.295 1.025 49 50.365 22.07 26.61 0.955 5041.175 36.09 21.755 0.975 51 34.825 45.785 18.4 0.99 52 30.17 52.8915.94 1 53 26.615 58.32 14.06 1.01 54 23.805 62.6 12.58 1.015 55 60.23517.6 21.22 0.95 56 66.775 14.635 17.64 0.95 60 51.135 29.88 18.015 0.9761 44.425 38.94 15.65 0.98 62 19.63 17.205 62.235 0.93 63 39.705 17.441.96 0.94 64 32.765 14.36 51.94 0.93 65 49.61 14.495 34.955 0.94 6642.175 12.325 44.57 0.93 67 20.35 35.675 43.01 0.965 68 16.72 29.31553.015 0.95 69 28.615 25.08 45.36 0.95 70 43.27 25.285 30.485 0.955 7137.505 21.915 39.635 0.945 72 17.24 45.34 36.44 0.98 73 14.565 38.29546.175 0.965 74 29.37 38.615 31.04 0.975 75 25.395 33.39 40.255 0.96 7638.37 33.63 27.03 0.97

TABLE 14 Peak wavelength of excitation and emission spectra onfluorescence measurement Excitation spectrum Emission spectrum PeakStrength Peak Intensity wavelength arbitrary wavelength arbitraryExample nm unit nm unit 38 449 8461 653 8479 39 449 7782 650 7832 40 4498470 654 8551 41 449 9725 658 9762 42 449 6171 679 6182 43 449 1279 6971245 44 449 7616 650 7763 45 449 7796 653 7854 46 449 6635 653 6685 47449 6106 654 6149 48 449 5857 654 5907 49 333 5168 636 5211 50 332 4271641 4342 51 330 4004 642 4046 52 335 3903 645 3954 53 335 3638 648 370354 337 3776 649 3799 55 316 2314 601 2348 56 407 1782 587 1906 60 4124304 616 4330 61 409 4080 607 4099 62 467 3130 649 3135 63 322 2461 6482461 64 449 1961 643 1996 65 316 3003 620 3003 66 319 3714 660 3714 67449 4534 650 4586 68 467 3072 647 3067 69 449 6422 650 6426 70 449 7785649 7856 71 449 4195 650 4179 72 449 4102 650 4095 73 461 2696 649 269374 449 9023 654 9146 75 450 5117 650 5180 76 322 6538 649 6538

Examples 77 to 84

As Examples 77 to 84 were prepared inorganic compounds havingcompositions in which D, E, and X Elements in theEu_(a)Ca_(b)D_(c)E_(d)X_(e) composition were changed.

Phosphors were prepared in the same manner as in Example 1 with theexception of the compositions shown in Tables 15 and 16. According tothe measurement of X-ray diffraction, it was confirmed that thesynthesized powders were powders containing inorganic compounds havingthe same crystal structure as that of CaAlSiN₃. When excitation andemission spectra of the synthesized inorganic compound were measured, asshown in Table 17, it was confirmed that they were red phosphors havingan emission peak in the range of 570 nm to 700 nm, which were excitedwith an ultraviolet ray or a visible light of 350 nm to 600 nm.

TABLE 15 Parameters for designed composition M A D E X Element ElementElement Element Element Eu Ca Si Ge Ti Hf Zr Al Y Sc N O Example a Valueb Value c Value d Value e Value 77 0.008 0.992 1 0.95 0.05 3 78 0.0080.992 1 0.9 0.1 3 79 0.008 0.992 1 0.8 0.2 3 80 0.008 0.992 0.95 0.05 13 81 0.008 0.992 1 0.97 0.03 3 0.045 82 0.008 0.992 0.97 0.03 1 3 0.0683 0.008 0.992 0.95 0.05 1 3 0.1 84 0.008 0.992 0.97 0.03 1 3

TABLE 16 Mixing composition of raw powder (unit: % by weight) M ElementA Element D Element E Element Example EuN Ca3N2 Si3N4 Ge3N4 TiO2 HfO2ZrN AlN YN Sc2O3 77 0.95 34.7 33.1 27.6 3.65 78 0.9 34 32.4 25.55 7.1579 0.9 32.6 31.1 21.8 13.7 80 0.95 34.95 31.65 3.25 29.2 81 0.95 35.333.65 28.6 1.5 82 0.95 35.25 32.6 1.75 29.45 83 0.9 33.5 30.35 7.2 28 840.95 35 32.4 2.35 29.3

TABLE 17 Peak wavelength and intensity of excitation and emissionspectra on fluorescence measurement Excitation spectrum Emissionspectrum Peak Intensity Peak Intensity wavelength arbitrary wavelengtharbitrary Example nm unit nm unit 77 449 6223 653 6380 78 449 4449 6534565 79 449 3828 650 3937 80 449 2022 645 2048 81 449 5143 647 5481 82450 2478 648 2534 83 449 3246 646 3303 84 449 8021 649 8050

Examples 85 to 92

As Examples 85 to 92 were prepared inorganic compounds havingcompositions in which M Element in the M_(a)Ca_(b)Si_(c)Al_(d) (N,O)_(e) composition were changed.

Phosphors were prepared in the same manner as in Example 1 with theexception of the compositions shown in Tables 18 and 19. According tothe measurement of X-ray diffraction, it was confirmed that thesynthesized powders were powders containing inorganic compounds havingthe same crystal structure as that of CaAlSiN₃. When excitation andemission spectra of the synthesized inorganic compound were measured, asshown in Table 20, it was confirmed that they were red phosphors havingan emission peak in the range of 570 nm to 700 nm other than thephosphor of Example 89, which were excited with an ultraviolet ray or avisible light of 350 nm to 600 nm. In Example 89, emission having a peakwavelength of 550 nm was observed.

TABLE 18 Parameters for designed composition X M Element A Element DElement E Element Element Mn Ce Sm Eu Tb Dy Er Yb Ca Si Al N O Example aValue b Value c Value d Value e Value 85 0.0027 0.9973 1 1 3 0.0027 860.0027 0.9973 1 1 3 0.0054 87 0.0027 0.9973 1 1 3 0.0041 88 0.00270.9973 1 1 3 0.0041 89 0.0027 0.9973 1 1 3 0.0047 90 0.0027 0.9973 1 1 30.0041 91 0.0027 0.9973 1 1 3 0.0041 92 0.0027 0.9973 1 1 3 0.0041

TABLE 19 Mixing composition of raw powder (unit: % by weight) M ElementA Element D Element E Element Example MnCO3 CeO2 Sm2O3 Eu2O3 Tb4O7 Dy2O3Er2O3 Yb2O3 Ca3N2 Si3N4 AlN 85 0.22 35.95 34.01 29.82 86 0.33 35.9133.97 29.78 87 0.34 35.91 33.97 29.78 88 0.341 35.91 33.97 29.78 89 0.3635.9 33.96 29.77 90 0.36 35.9 33.97 29.78 91 0.37 35.9 33.96 29.77 920.38 35.89 33.96 29.77

TABLE 20 Peak wavelength and intensity of excitation and emissionspectra on fluorescence measurement Excitation spectrum Emissionspectrum Peak Intensity Peak Intensity wavelength arbitrary wavelengtharbitrary Example nm unit nm unit 85 449 1629 631 1703 86 466 2453 6162592 87 310 3344 651 3344 88 449 6933 641 7032 89 255 2550 550 2550 90248 7459 580 7509 91 449 1572 631 1630 92 448 821 640 833

Example 101

As raw powders were used an Eu₂O₃ powder, a Ca₃N₂ powder having anoxygen content of 9% by mol which is represented by mol number of oxygenrelative to the total mol number of nitrogen and oxygen, an Si₃N₄ powderhaving an oxygen content as above of 2% by mol, and an AlN powder havingan oxygen content as above of 2% by mol. Respective powders were weighedso as to be the metal element composition ratio (mol ratio) ofEu:Ca:Al:Si=0.008:0.992:1:1 and mixed to obtain a raw mixed powder. Theoxygen content represented by mol number of oxygen relative to the totalmol number of nitrogen and oxygen in the raw mixed powder was 5% by mol.In this connection, the Ca₃N₂ powder is a powder obtained by allowingoxygen to exist using raw materials to be baked containing only adesired concentration of oxygen, the Si₃N₄ powder is a powder obtainedby allowing oxygen to exist using raw materials to be baked containingonly a desired concentration of oxygen, the AIN powder is a powderobtained by allowing oxygen to exist using raw materials to be bakedcontaining only a desired concentration of oxygen.

The raw mixed powder was placed in a crucible made of boron nitridewithout compression so as to be a bulk density of 0.35 g/cm³ and wasbaked at 1600° C. for 10 hours in a highly pure nitrogen atmospherecontaining an oxygen concentration of 10 ppm or less at a nitrogenpressure of 1.1 atm using an electric furnace. At this time, the oxygenexisting ratio in the raw material at baking is 5% by mol based on thecalculation from the oxygen concentration in each raw material and themixing ratio of each raw material.

As a result of identification of the crystal phase formed in theresulting phosphor by powder X-ray diffraction method, it was confirmedthat CaAlSiN₃ family crystal phase was formed. When fluorescenceproperties of the phosphor were measured by excitation with a wavelengthof 465 nm using a fluorescence spectrophotometer, the resulting phosphorshowed a peak intensity of 128 in the case that the peak intensity of acommercially available yttrium aluminum garnet-based phosphor activatedwith Ce was regarded as 100, showing a high emission intensity, and ared light having a peak wavelength of 652 nm was observed. Moreover, 20mg of the obtained phosphor sample was charged into a tin capsule, whichwas then placed in a nickel basket. Then, when the concentrations ofoxygen and nitrogen in the powder sample were analyzed using a TC-436Model oxygen and nitrogen analyzer manufactured by LECO, in the total ofnitrogen and oxygen, it contained 94% by mol of nitrogen and 6% by molof oxygen.

Example 102

A phosphor powder was obtained in the same manner as in Example 101except that EuF₃ was used instead of Eu₂O₃. The oxygen contentrepresented by mol number of oxygen relative to the total mol number ofnitrogen and oxygen in the raw mixed powder was 5% by mol. Moreover, theoxygen existing ratio in the raw material at baking is 5% by mol basedon the calculation from the oxygen concentration in each raw materialand the mixing ratio of each raw material.

As a result of identification of the crystal phase formed in theresulting phosphor by powder X-ray diffraction method, it was confirmedthat CaAlSiN₃ family crystal phase was formed. When fluorescenceproperties of the phosphor were measured by excitation with a wavelengthof 465 nm using a fluorescence spectrophotometer, the resulting phosphorshowed a peak intensity of 114 in the case that the peak intensity of acommercially available yttrium aluminum garnet-based phosphor activatedwith Ce was regarded as 100, showing a high emission intensity, and ared light having a peak wavelength of 650 nm was observed. Moreover, 20mg of the obtained phosphor sample was charged into a tin capsule, whichwas then placed in a nickel basket. Then, when the concentrations ofoxygen and nitrogen in the powder sample were analyzed using a TC-436Model oxygen and nitrogen analyzer manufactured by LECO, in the total ofnitrogen and oxygen, it contained 95% by mol of nitrogen and 5% by molof oxygen.

Example 103

A phosphor powder was obtained in the same manner as in Example 101except that EuN was used instead of Eu₂O₃ and the baking time waschanged to 2 hours. The oxygen content represented by mol number ofoxygen relative to the total mol number of nitrogen and oxygen in theraw mixed powder was 5% by mol. Moreover, the oxygen existing ratio inthe raw material at baking is 5% by mol based on the calculation fromthe oxygen concentration in each raw material and the mixing ratio ofeach raw material.

As a result of identification of the crystal phase formed in theresulting phosphor by powder X-ray diffraction method, it was confirmedthat CaAlSiN₃ family crystal phase was formed. When fluorescenceproperties of the phosphor were measured by excitation with a wavelengthof 465 nm using a fluorescence spectrophotometer, the resulting phosphorshowed a peak intensity of 112 in the case that the peak intensity of acommercially available yttrium aluminum garnet-based phosphor activatedwith Ce was regarded as 100, showing a high emission intensity, and ared light having a peak wavelength of 649 nm was observed. Moreover, 20mg of the obtained phosphor sample was charged into a tin capsule, whichwas then placed in a nickel basket. Then, when the concentrations ofoxygen and nitrogen in the powder sample were analyzed using a TC-436Model oxygen and nitrogen analyzer manufactured by LECO, in the total ofnitrogen and oxygen, it contained 95% by mol of nitrogen and 5% by molof oxygen.

Example 104

A phosphor powder was obtained in the same manner as in Example 101except that EuN was used instead of Eu₂O₃, the nitrogen pressure waschanged to 10 atm, and the baking time was changed to 2 hours. Theoxygen content represented by mol number of oxygen relative to the totalmol number of nitrogen and oxygen in the raw mixed powder was 5% by mol.Moreover, the oxygen existing ratio in the raw material at baking is 5%by mol based on the calculation from the oxygen concentration in eachraw material and the mixing ratio of each raw material.

As a result of identification of the crystal phase formed in theresulting phosphor by powder X-ray diffraction method, it was confirmedthat CaAlSiN₃ family crystal phase was formed. When fluorescenceproperties of the phosphor were measured by excitation with a wavelengthof 465 nm using a fluorescence spectrophotometer, the resulting phosphorshowed a peak intensity of 109 in the case that the peak intensity of acommercially available yttrium aluminum garnet-based phosphor activatedwith Ce was regarded as 100, showing a high emission intensity, and ared light having a peak wavelength of 650 nm was observed. Moreover, 20mg of the obtained phosphor sample was charged into a tin capsule, whichwas then placed in a nickel basket. Then, when the concentrations ofoxygen and nitrogen in the powder sample were analyzed using a TC-436Model oxygen and nitrogen analyzer manufactured by LECO, in the total ofnitrogen and oxygen, it contained 95% by mol of nitrogen and 5% by molof oxygen.

The results of Examples 101 to 104 are summarized in Table A.

TABLE A Fluorescence properties Baking conditions (465 nm excitation)Mixing ratio Oxygen Peak of raw materials Bulk existing ratio inintensity Peak (molar ratio) density Temperature Time Pressure rawmaterial Eu raw [relative wavelength Eu Ca Al Si [g/cm³] [° C.] [hour][atm] [% by mol] material value] [nm] Example 0.008 0.992 1 1 0.35 160010 1.1 5 Eu₂O₃ 128 652 101 Example 0.008 0.992 1 1 0.35 1600 10 1.1 5EuF₃ 114 650 102 Example 0.008 0.992 1 1 0.35 1600 2 1.1 5 EuN 112 649103

The following will explain the lighting equipment using a phosphorcomprising the nitride of the invention. FIG. 14 shows a schematicstructural drawing of a white LED as a lighting equipment. Using a blueLED 2 of 450 nm as a light-emitting element, the phosphor of Example 1of the invention and a yellow phosphor of Ca-α-sialon:Eu having acomposition of Ca_(0.75)EU_(0.25)Si_(8.625)Al_(3.375)O_(1.125)N_(14.875)are dispersed in a resin layer to form a structure where the blue LED 2is covered with the resulting resin layer. When electric current ispassed through the electroconductive terminals, the LED 2 emits a lightof 450 nm and the yellow phosphor and the red phosphor are excited withthe light to emit yellow and red lights, whereby the light of LED andthe yellow and red lights are mixed to function as a lighting equipmentemitting a lamp-colored light.

A lighting equipment prepared by a combination design different from theabove combination may be shown. First, using an ultraviolet LED of 380nm as a light-emitting element, the phosphor of Example 1 of theinvention, a blue phosphor (BaMgAl₁₀O₁₇:Eu), and a green phosphor(BaMgAl₁₀O₁₇:Eu,Mn) are dispersed in a resin layer to form a structurewhere the ultraviolet LED is covered with the resulting resin layer.When electric current is passed through the electroconductive terminals,the LED emits a light of 380 nm and the red phosphor, the greenphosphor, and the blue phosphor are excited with the light to emit red,green, and blue lights, whereby these lights are mixed to function as alighting equipment emitting a white light.

A lighting equipment prepared by a combination design different from theabove combination may be shown. First, using a blue LED of 450 nm as alight-emitting element, the phosphor of Example 1 of the invention and agreen phosphor (BaMgAl₁₀O₁₇:Eu,Mn) are dispersed in a resin layer toform a structure where the blue LED is covered with the resulting resinlayer. When electric current is passed through the electroconductiveterminals, the LED emits a light of 450 nm and the red phosphor and thegreen phosphor are excited with the light to emit red and green lights,whereby the blue light of LED and the green and red lights are mixed tofunction as a lighting equipment emitting a white light.

The following will explain a design example of an image display unitusing the phosphor of the invention. FIG. 15 is a principle schematicdrawing of a plasma display panel as an image display unit. The redphosphor of Example 1 of the invention, a green phosphor (Zn₂SiO₄:Mn),and a blue phosphor (BaMgAl₁₀O₁₇:Eu) are applied on the inner surface ofcells 11, 12, and 13, respectively. When electric current is passedthrough electrodes 14, 15, 16, and 17, a vacuum ultraviolet ray isgenerated in the cells by Xe discharge and thereby the phosphors areexcited to emit red, green, and blue visible lights. The lights areobserved from the outside through the protective layer 20, thedielectric layer 19, and the glass substrate 22, whereby the unitfunctions as an image display.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof.

The present application is based on Japanese Patent Application No.2003-394855 filed on Nov. 26, 2003, Japanese Patent Application No.2004-41503 filed on Feb. 18, 2004, Japanese Patent Application No.2004-154548 filed on May 25, 2004, and Japanese Patent Application No.2004-159306 filed on May 28, 2004, and the contents are incorporatedherein by reference.

INDUSTRIAL APPLICABILITY

The nitride phosphor of the invention exhibits emission at a longerwavelength as compared with conventional sialon and oxynitride phosphorsand is excellent as a red phosphor. Furthermore, since luminancedecrease of the phosphor is small when it is exposed to an excitationsource, it is a nitride phosphor suitably used for VFD, FED, PDP, CRT,white LED, and the like. Hereafter, it is expected that the phosphor iswidely utilized in material design in various display units and thuscontributes development of industry.

What is claimed is:
 1. Light-emitting equipment, comprising at least onelight source, the light source comprising at least one light-emittingsource and a phosphor, wherein: the light-emitting source emits a lighthaving a wavelength of 330 to 500 nm; and the phosphor comprises atleast one of a nitride phosphor comprising at least one of CaAlSiN₃activated with Eu and (Ca,Sr)AlSiN₃ activated with Eu.
 2. Thelight-emitting equipment according to claim 1, wherein thelight-emitting source emits a light having a wavelength of 420 to 500nm.
 3. The light-emitting equipment according to claim 2, wherein thephosphor further comprises at least one of: a phosphor having anemission peak at a wavelength of 500 to 570 nm; and a phosphor having anemission peak at wavelength of 550 to 600 nm.
 4. The light-emittingequipment according to claim 1, wherein the light-emitting source emitsa light having a wavelength of 330 to 420 nm.
 5. The light-emittingequipment according to claim 4, wherein the phosphor further comprises:a phosphor having an emission peak at a wavelength of 420 to 500 nm anda phosphor having an emission peak at a wavelength of 500 to 570 nm. 6.The light-emitting equipment according to claim 1, wherein thelight-emitting equipment is lighting equipment.
 7. The light-emittingequipment according to claim 1, wherein the light-emitting equipment isan image display unit.
 8. The light-emitting equipment according toclaim 1, wherein the nitride phosphor comprises a crystal phase having acrystal structure belonging to the Cmc2₁ space group.
 9. Thelight-emitting equipment according to claim 1, wherein the nitridephosphor comprises Ca and Sr in amounts satisfying:0.02≤(number of atoms of Ca)/{(number of atoms of Ca)+(number of atomsof Sr)}<1.
 10. The tight-emitting equipment according to claim 1,wherein, when irradiated by an excitation source, the nitride phosphoremits light having a peak emission intensity at a wavelength of from 570nm to 700 am.
 11. The light-emitting equipment according to claim 1,wherein, when irradiated by an excitation source, the nitride phosphoremits light having a color satisfying:0.45≤x≤0.7 as a value of (x, y) the CIE chromaticity coordinates. 12.The light-emitting equipment according to claim 1, wherein the nitridephosphor comprises impurity elements of Fe, Co, and Ni in an amount of500 ppm or less.
 13. The light-emitting equipment according to claim 1,wherein: the nitride phosphor comprises an inorganic compound and afurther crystal phase or amorphous phase; and the inorganic compound ispresent in an amount of at least 20% by weight based on a total weightof the inorganic compound and the further crystal phase or amorphousphase.
 14. Light-emitting equipment, comprising at least one lightsource, the light source comprising at least one light-emitting sourceand a phosphor, wherein: the light-emitting source emits a light havinga wavelength of 420 to 500 nm; the phosphor comprises a phosphor havingan emission peak at a wavelength of 500 to 570 nm or a phosphor havingan emission peak at a wavelength of 550 to 600 nm; and the phosphorcomprises CaAlSiN₃ activated with Eu or (Ca,Sr)AlSiN₃ activated with Eu.